Hardware
This should be one of the more important aspects of the Lion experience. Lion is designed strictly for 64-bit x86 CPUs, so if you have any Mac that has an Intel Core2Duo and up, you're covered. Lion will install and run. Folks still running first gen Intel CPUs or PowerPC Macs (like a G5 for instance) are out of luck. Apple no longer supports that architecture in the realm of new OS X. Assuming you have an Intel based Mac, the next problem is RAM. The minimum requirement for memory is 2GBs. I'm telling you that you would want at least 4GBs. Macbook Pro users of the 15 - 17inch kind shouldn't have to worry about that since most of them come with 4GBs already. I highly stress that you upgrade if your Mac can only run DDR2 ram and you can find out by doing the following:
Click on the Apple and select "About this Mac"
Once that window opens up, click on "More Info"
This window will show up. Click on the highlighted Memory page, and look under 'Type'. It will tell you whether your computer uses DDR2 or 3.
PEOPLE WITH LION ALREADY INSTALLED: When you click on "More Info" the top screen will pop up and show what you have. Click on the "Memory" tab to see exactly what your computer can accept.
DDR2 RAM is easily available at Best Buy. If you know that your computer can take DDR3 RAM, I recommend that you have at least 4GBs. If you have the means to install more than 4GBs, DO IT! Realize that for most MacBooks (that are not Pro line 15-17's) share the system RAM with the video card, and it uses more if you're doing more graphic intensive work. You can never have enough RAM, so get as much as you can.
Speaking of GPUs, there is no minimum requirement for what kind of video card you have, but that doesn't mean there isn't a difference. Basically, if you have a Macbook Pro (again, 15 or 17in.) or a Mac Pro, you're completely covered in this department. They use dedicated memory, and older Macbook Pro models have 2 GPUs built in. There isn't much you can do about the Video card, but chances are that you will be fine in the first place. If you run a Mac Pro, you should check what kind of card you have (same method as checking RAM), and if possible, replace it with a newer card. Chances are that you probably won't have to do that, but Mac Pro owners have the ability to change their GPUs, so if you have an older build of the Pro tower, now is a good time to replace your GPU.
NEW MAC OWNERS (late 2010 - present): Your chances of having a CPU/GPU/RAM issue is slim to none. Your Macs are already optimized for Lion, especially if you own the new Macbook Air or the brand new version of the Mac Mini. You shouldn't have to worry too much about the hardware (that's what she said!).
Hard Drive Woes..
One thing that a lot of Mac owners should worry about (old and new) is Hard Drive speed. A lot of people tend to buy their Macbooks/iMacs with HDDs that spin at 5400RPMs. Apple does this so they can have an extra option for either a 7200RPM drive or a Solid State Drive and charge you for it. This applies to 15-17in. Macbook Pros. All 13in. and the low end 15in. Macbook Pros will charge extra for upgrading to a 7200RPM drive (up to $100) while the high end 15in. and 17in. Pro come with a 750GB 5400RPM with the option of selecting a 500GB 7200RPM drive for free. Apple also charges extra for a 7200RPM drive for the new Mac Mini's. If you own a newer iMac or Mac Pro, all models come with a 7200RPM drive, and if you own a 2nd / current gen Air, you have a SSD drive, so no worries there.
When you buy online, you can customize your build. Typically, Apple gives you the slowest drive and charges for a faster drive. Prices shown doesn't necessarily reflect prices at retails like Best Buy or sites like Newegg.
Most older Macs most likely have a 5400RPM drive, and it hinders performance in Lion quite a bit. I suggest that you upgrade to at least a 7200RPM drive. If you have the means to get an SSD, do it. Basically, a faster HDD means better performance.
Minor stuff: Before the techies jump on me saying that I didn't mention anything about cache, lemme tell you that this is something that you shouldn't have to worry about. Cache is like RAM for your hard drive. The concept is that the more you have, the faster you access the data. In reality, the difference between a 32MB cache and a 16MB is slim to none. My rule of thumb with cache is that if you are factoring cache into your purchase, go with the 32MB. In fact, it's all I see nowadays, but if there are only 16MBs cache drives, just get it. Just as long as that drive spins at 7200RPMs.
My Hard Drive Recommendations
For laptops, I suggest my current HDD: a Seagate Momentus XT Hybrid. It's a 7200RPM 500GB+4GB SSD. A hybrid drive is a cheap mans SSD. It uses the SSD memory to store frequently used data. For instance, it uses the SSD portion for my boot up sequence, as well as apps like Chrome, Safari, and iTunes (apps that I use often). Think of it as a large and fast cache. with the Momentus, I have a boot time of 18 seconds. It also gave me a performance boost over my 160Gb 5400RPM stock drive (obviously.) The performance to price ratio ($130) is reason enough to get this drive. Compare that price and size to a 512GB SSD (cheapest being $839.99 @ Newegg). Of course, you won't get the exact performance of an SSD, but you're sure as hell getting something that's faster than a regular 7200RPM drive
Seagate Momentus XT (box misprint. It's a 32MB Cache HDD).
Installation
Whether you're covered in the hardware department, or if you're just going to wing it, the biggest pre-install step that you should do is clean install your Lion installation. This mainly applies to the Mac owners who had their Macs for a couple years now. If your Mac is fairly new, you may be able to pull an upgrade off. Anyway, to start a baseline off, we'll go as far back as my current Mac (Macbook 13in. Aluminum, late 2008). My method was rather tedious, and took about over 4 hours to finish up. This mostly because one, OS X Lion is currently download-only through the App Store, two, I never took advantage of Time Machine, so I had to transfer all of my files to my PC because my only external drive is using a Windows-Only filesystem (NTFS..which is read only on Macs), three, I took the scenic route and formatted my new drive to a filesystem that was windows and mac compatible in order to transfer all my files from one computer to another, and four, I wasn't in a rush. As soon as I installed the new drive to the Macbook, I used my extra copy of Snow Leopard to format the drive to the proper filesystem, reinstalled Snow Leopard, reinstalled iLife (09' and 11' since 11' didn't have iWeb), re-downloaded all updates, re-download Lion on the App Store and finally, installing it. Sounds horrendous, right?
There is a easier way, but it's still a little time consuming. I will say, that it'll be worth it though! Here is how to do it:
Pre-Install -
If you use Time Machine: back up what you want...simple, right
If you're not using Time Machine: either have an extra drive available to transfer files, or a flash drive, or a DVD-R..whatever (unless you don't have a need to backup).
Time Machine is your best friend.
Installation Time
Use your Recovery disk/Recovery flash/or OS installation disk to wipe and format your current drive (or new drive), and reinstall that OS (real easy stuff btw.).
When your OS is done setting up, click on the Apple icon and "Software Update"
After it checks for software updates the above window will show. Click on the install button, follow the instructions and just let it do it's thing.
After that is done, run the App Store, click on the giant Mufasa on the front page, and cough up the $29.99.
IF YOU ALREADY OWN LION: click on the "Purchases" tab and you'll find the install.
Lion is 3.5GBs and it'll take about an hour to download + an installation time of about 30 minutes.
Now, the reason why it takes this long to do a clean install is because there is currently no physical medium with Lion. Lion doesn't come in a disk, and I can imagine a much more tedious procedure of getting the App Store download on another medium. Tedious enough for a casual user to discourage them from trying. There is hope on the way, but it comes at a price. Apple will release a retail version in the form of a flash drive, but it will sell for $69. The clear advantage to this version is that once you backed up your wanted data (and install your new drive.), all you gotta do is plug in the USB, wipe the drive and install Lion. A process that'll take less than an hour.
Whether you wait and spend more for the flash drive version or not, I stand by the fact that a clean installation is still the way to go. Yeah, there are drive cloning methods, but you're really just taking the problems that you had on your previous OS and placing them into Lion. I know Mac users suffer from some sort of slow down after a couple years of use. Like a Windows installation, a clean slate is the best way to use your new OS installation. If you're proactive in finding other alternates, there is most likely a solution for putting the App Store version on a disk already.
<<<After installation, initial setup, and restoring your data, reset your Mac a couple times. Just do it.>>>
Using Lion
You need get acquainted with some of the features that come out of the box. The main features I do use are the features that were bragged about during the keynote. I will get there but first, an AppleID initial setup.
Syncing your AppleID to your account
First, click on your Name and select "User & Group Preferences"
Under AppleID, enter your credentials so you'll be sync'd with apps using your AppleID.
Setting you AppleID up will set you up for the apps that require it. I also think that this is to set your account up for the upcoming iCloud service.
Using Launchpad
To some in the Mac community, Launchpad is merely a feature to humor the users who are heavily familiar with iOS products, but are new to OS X. A gimmick that is to be shunned because we already have the Dock. In reality, the Dock and Launchpad switch roles. In order to have apps on your dock, you have to install the app, find the app in your applications folder, and drag it to the Dock. Launchpad brings every program you installed as well as access to Utilities in one gesture. That is one step less, and I welcome that. The Dock still serves it's purpose as a quick launcher for the apps that I use often, but the fact that you can you can use your index (or middle) finger and gesture swipe to the lower right corner to bring ALL of your apps up shows that Apple is trying to take the littlest details and make it easier to do. To top it off, If you're using a single desktop (not recommended anymore) to run multiple apps, the Dock can act as a task switcher (unless you know cmd+tab) since running apps will still show up on the Dock.
Launchpad functions just like an iOS device. A single finger swipe to the lower right corner (or clicking on the icon...you lame) will bring Launchpad up and two finger swipes to either the left or right will move the pages. You can jiggle the icons, but click and dragging also works fine. Creating subfolders works the same way as iOS as well.
Launchpad
Creating a subfolder and naming it.
Full Screen apps.
As part of making Lion iOS user-friendly, they decided to use a full screen feature for most apps. Typically, browsers always had this feature, but Apple wanted to take it to their other apps to give it a iPad app look.
Certain apps like iTunes and Safari will create it's own separate window in order to keep your active desktops clean.
Safari
Chrome
iTunes
Macs New Best Friend: Mission Control
A 3 finger swipe upward will bring up Mission Control. Mission Control is the spawn of Spaces and Expose. This demon child will bring you Dashboard, all active desktops, full screen apps, and depending on what desktop you're on, all opened apps and folders on that one desktop. You can then move those folders/apps to another available desktop or place it on a new desktop by dragging it to the upper right corner. The purpose is for organizing your would be multi-tasking habits. Switching between desktops is as simple as swiping 3 fingers left or right. Back when Spaces and Expose was around, they were the features that I used the most. Mission Control definitely just made it a lot easier, and I was hoping that Apple combined the latter. I'm glad there were like-minded folk who thought the same.
Mission Control (notice that Safari and iTunes have their own spaces.)
Mission Control will have multiple apps and folders on one desktop organized when you select the desktop.
When you drag a folder/app, you can either drop it in another desktop, or drop it in a new desktop as pictured on the top.
You can also spawn another desktop by simply bringing your mouse to the upper right corner of the screen.
Swiping between desktops.
Wrap Up
This is going to be longer than I thought. Part two will cover the new features for Safari, Mail, Address Book, iCal, as well as the uses of Versions. Of course, if you want to be proactive about it, you can watch the WWDC 2011 Keynote and have Steve and the rest of the creative leads show you these and the other new features of Lion as well as iOS 5. this is the link for the stream: http://events.apple.com.edgesuite.net/11piubpwiqubf06/event/
You can also search and download it on iTunes keyword: Apple Keynotes.