Only Apple knows the release date -- the latest rumors have it as July 6, maybe July 14 -- but you can prep your Mac now to make the upgrade go faster and more smoothly.
Make sure your Mac can handle Lion
Lion's system requirements are slightly different from Snow Leopard's, so you need to verify that your Mac can run the new operating system.
Select "About This Mac" from the Apple menu, and look at the "Processor" and "Memory" items in the resulting pop-up.
Your Mac must have an Intel Core 2 Duo, Core i3, Core i5, Core i7 or Xeon CPU for a processor.
As for memory, you need 2GB or more.
You can't do much about a processor that won't run Lion, but it's easy and inexpensive to boost memory in a Mac. Crucial, one of the largest RAM sellers, prices a 2GB upgrade for a mid-2008 MacBook (the low-end model came with just 1GB stock) at $30 or a 4GB upgrade for $60.
You must be running Snow Leopard
According to Apple, you can only upgrade to Lion from Mac OS X 10.6, aka Snow Leopard.
For now, Apple hasn't spelled out any direct upgrade path for users running Leopard, or Mac OS X 10.5, so if you're using that 2007 operating system, you'll first need to migrate to Snow Leopard, the OS Apple launched in August 2009.
Apple and others, including Amazon.com, sell a single-license copy of Snow Leopard for $29, or $49 for a five-license Family Pack.
For those still running Mac OS X Tiger and who have a Mac that meets the processor and memory requirements, the only option at the moment is to update to Snow Leopard using the $129 Mac Box Set.
A five-license Mac Box Set sells for $179.
Update to Mac OS X 10.6.8
Having Snow Leopard on your Mac isn't enough for Lion: You need to update the OS to version 10.6.8, which Apple released June 23.
Apple has said only that 10.6.8 "enhance[s] the Mac App Store to get your Mac ready to upgrade to Mac OS X Lion," referring to the Mac software download store that Snow Leopard has supported since January and that Apple will use to distribute Lion.
Select "Software Update" from the Apple menu and install 10.6.8.
Obtain an Apple ID
To download Lion from the Mac App Store, you'll need an Apple ID.
You may already have one -- that's what you use to sign in to iTunes, for instance -- but if you don't, you can create one here by providing an email address, password and other information.
(Hint: Use a different password for your Apple ID than you do for the email address you give; that way, if either your email provider or Apple is hacked, there's less chance that the criminals can access both.)
Prep the Mac App Store with a payment option
You'll also need to provide a payment method for Lion on the Mac App Store.
Most users will have assigned a credit card to their Apple ID, but if you don't have a credit card -- or don't want to give one to Apple -- you can buy an iTunes gift card and transfer its funds to the Mac App Store.
To do that, click on one of the first three icons at the top of the Mac App Store application -- Featured, Top Charts or Categories -- then click "Redeem" under the "Quick Links" section at the upper right.
Enter the gift card code in the field provided, then click the Redeem button.
Note: Apple Gift Cards, which are redeemable only at Apple retail stores and its online store, cannot be used for the Mac App Store.
Back up your Mac
To be safe, back up your Mac using Time Machine (or other backup software) and an external drive so that you can restore the system to Snow Leopard if Lion won't install or somehow cripples the machine.
And make sure your Snow Leopard installation DVD is handy so that you can use it to boot your Mac if Lion bricks it.
Check application compatibility
Because Lion won't let you install Rosetta, the software emulator that allows Intel-based Macs to run software compiled for the PowerPC processor, those older applications won't work on the new OS.
You can see which PowerPC applications are on your Mac by clicking "About This Mac" under the Apple menu, then clicking the "More info" button at the bottom of the pop-up to bring up the System Profiler.
Select "Applications" from the "Software" category on the left-hand pane of the System Profiler. Click on the "Kind" column to sort it, then scroll until you find those apps that show "PowerPC" or "Classic." (The latter did not run on Snow Leopard either.)
On our test iMac, only a handful of apps were labeled as PowerPC, including a pair associated with Office for Mac 2008 that convert charts and Excel workbooks so they can be opened, edited and saved in earlier versions of Microsoft's suite, such as Office for Mac 2004 and Office 2003 on Windows.
You can also browse a massive list at RoaringApps that notes which Mac programs work with Lion's earlier developer builds, which don't and which have trouble with the new OS.
Applications that have been tested typically include users' comments that provide additional information on what worked and what didn't on dev versions of Lion.
It's worth your time to brush up on the apps you can't live without by reading the comments: Forewarned is forearmed.
Scout out a fast connection if you don't have one
Because Lion will be delivered only through the Mac App Store, users with a dial-up connection, or one that's heavily metered, such as a satellite-based link, will have to score the upgrade away from home.
Apple has said customers are welcome to use the Wi-Fi connection in its retail stores to download Lion, but any public hotspot will do.
Another option is to take your Mac notebook to the home of a friend who has a fast connection, or to your workplace.
Mac desktops are another matter: No one will want to haul their 27-in. iMac around town.
It's unclear how those customers will be able to obtain Lion. Although Apple has told schools and businesses that they will be allowed to download Lion once, then run the resulting installer on each Mac, the company hasn't confirmed that consumers will be able to do the same.
Wash, rinse, repeat
Prep each Mac you own, then wait for Lion to appear in the Mac App Store.
Apple has given advance notice before of an operating system's impending release, but we're not certain it will this time, since there's no need for customers to go to a store or order online and wait for the delivery truck.
The company will tell you when Lion is available if you give it your email address.
When Lion hits the Mac App Store, you can download the upgrade to each Mac you own for the one-time fee of $29.99 by using the same Apple ID.
Purchase Lion with your preferred Apple ID, download and install to the first Mac, then on all others, sign in to the Mac App Store using that same email address and password to download the upgrade.
It doesn't matter if some of the Macs in the household -- a child's, spouse's or partner's Mac, for example -- usually rely on a different Apple ID; just sign in to the Mac App Store with the Apple ID that was used to purchase Lion, and you can download a second copy (and a third and a fourth and so on) gratis.
That Apple ID has to be entered on these Macs only this one time; unlike other apps sold in the Mac App Store, Lion will rely on the operating system's own Software Update mechanism for future feature enhancements and security fixes.
Optional: Buy a Magic Trackpad for your desktop Mac
It's strictly optional, but the slew of touch gestures built into Lion -- scrolling pages, switching between apps, zooming -- will be unavailable to those armed with an iMac, Mac Pro or Mac Mini.
Although the $69 Magic Mouse supports gestures, our choice is the same-priced Magic Trackpad.