BYTE -- Before you download Apple OS X Lion, you've got to prepare your system.
This will be the first time Apple releases a major OS X update entirely through its Mac App Store. That means no DVD for you. It also means system requirements are a little more stringent. This update leaves a lot of legacy hardware behind -- there is zero PowerPC support, for example.
So first, make sure your Mac has what it takes. If you're already running OS X 10.6.8 Snow Leopard, you're good to go. Well, almost good to go. Macs using Intel's Core Solo or Core Duo won’t support Lion. But if your system includes a Core 2 Duo, Core i3, Core i5, Core i7, or Xeon Intel processor, you're ready CPU-wise.
Make sure your system has at least 2GB RAM. I recommend 4GB for best results. Check your processor type and amount of system memory by going to Finder and clicking on the Apple menu. Now click on About This Mac. A window will open that looks like this:
Check compatibility for your applications, too. Contact the software developers behind your favorite applications to find out what will work with Lion. If the software is "universal" and supports Intel CPUs, you’ll be fine. If you need an update, now’s the time to do it.
Check out crowd-sourced compatibility information about a plethora of OS X applications at RoaringApps.com.
You must find all your applications that require PowerPC or Rosetta support. OS X Lion supports neither and will effectively kill off anything that amounts to PowerPC support. OS X no longer includes Rosetta, the translator the Mac uses to translate Power PC code to run on Intel processors.
It's easy to find the applications on your system that require Rosetta or a PowerPC processor. Go to Finder and click on the Apple menu. Now click on About This Mac. A window will open that looks like this:
Click on the button labeled More Info. System Profiler will open a new window.
Click Software on the left hand side of the System Profiler window. Select Applications.
Now drag the window to open it wider towards the right expanding the window until you see a column heading that says Kind. Click Kind to sort applications.
Scroll through the list and find all applications that say PowerPC under the Kind heading.
Before upgrading, check the health of your startup drive. Head to /Applications/Utilities and select your startup drive, click the First Aid tab. Click Verify Disk Permissions.
If Disk Utility reports problems, reboot either from the DVD set that came with your Mac or another bootable volume on DVD or USB. Select Repair Disk Permissions
Before you upgrade to Lion, make a really good backup. I recommend you make a mirror image of your Mac's startup drive. For this, you'll need an external USB, FireWire or Thunderbolt hard drive that is as large as or larger than your startup drive.
The best kind of Mac backup is a clone of the source drive and bootable, too. Shirt Pocket’s SuperDuper is one of my favorite utilities for this kind of backup. It's available for free and under $30 for the full version, which is what I recommend.
If you really want to get the best use out of new features like Mission Control, Launchpad, and full-screen applications on OS X Lion that use the enhanced mutli-touch gesture support in the new OS, think about getting the Magic Trackpad.
That's an optional gadget, of course, but you'll really like it with OS X Lion. Or, if you're using a Mac with a built-in trackpad, you're good to go.
I've upgraded three Macs up to OS X Lion and so far I haven't encountered any screaming problems. Just make sure you get everything prepared before you make the leap.