How do you check if a game works on your computer

Typically, officially released games on storeshelves will have the system requirements listed on the box telling you the specifications. Sometimes they're listed as a simple icon on the front of the package, otherwise you may have to hunt for them. For example, Blizzard's Battlechests have their system requirements listed next to the barcode. In a worst-case scenario, if the requirements aren't listed, it may not work on your computer, so you should research it before you buy.

System Specifications to consider:
Mac OS or PC OS: Although Macs are PCs, PC's are generally the category that encompasses Windows. Assuming you have only one or the other and you don't have the means to emulate or run the other OS (via CrossOver, or BootCamp or what-have-you) the game will not work if you have the wrong one.
OS Version: After Mac OS versions increase by digits, while Windows versions increase by name (10.3.9 to 10.6.2 and XP to Vista respectively), if you have a version that's too old, it won't play.
PowerPC or Intel: Though not always listed since "PC"s are generally Intel-based and Mac just recently made the switch, if you have an Intel-only game, but you have a PowerPC Mac, it won't play.
RAM and Space: The game takes up resources to run and requires space to fit on your computer, if it lacks RAM, the game will run slowly, if it lacks Space, you won't be able to install it on your computer.
Video Card and Sound Card: While generally dismissible on higher-end computers, it's worth mentioning that if your computer is not up to snuff in these departments, Audio and Visual quality could take a hit, lag your game, or worse, refuse to work.
Connection Speed: Online games will require player's computers to be able to send necessary information fast enough to be received by the other players and game server, if you have a good computer, or you don't have internet, or have no plans of playing online, you can ignore this one.
Disk Drive: If you don't have a disk drive...

Internet Connection: Some established gaming companies have put major lockouts on newer computer game titles. If you don't have an internet connection, or your connection flickers at any point during gameplay (even if it's not online play), the game will lock you out. These games should be avoided as a rule.



Simply, just check the system requirements, if your computer has the minimal necessary operating system (OS) you should be fine, and if you're running a new Intel Mac, keep in mind that most games that have been released aren't equipped to play on it yet.