1. Check ur motherboard compatibility.
2. u might have an AGP, PCI, or PCI-e express.
3. Check your power supply, u might wanna buy a new one.
4. Check you moniter's resolution. Know it since u will game on it.
5. Check your motherboard's specs, Nvidia (SLI), ATI (CROSSFIRE), or both (X58 chipsets).
6. If u have either i suggest u stick to it. Dont buy Nvidia cards on crossfire motherboard or viseversa.
7. Now this is the most important part PEOPLE CHECK YOUR WALLET.
Now after you have checked your wallet there is still 1 Tricky thing NEW GRAPHIC CARDS ON OLD CPU.
Having an old cpu with a high-end card can be really frustrating as the card will be much faster than ur cpu.
Either upgrade or ATLEAST overclock.
Before u buy ur card add RAM increase ur RAM atleast have 4 gigs.
Upgrade your OS to a 64-bit version. If u have 4 gigs of ram and u add the card u will lose RAM, as if u added nothing.
NOW, u should not judge a card on its performance if it fails with the NOTORIOUS games i.e. stalker clearsky crysis and crysis warhead.
NOW just check TomsHARDWARES Best Graphics Card FOR THE MONEY.
Step (8) depends on the game, some have low CPU loads, but heavy graphic loads, and others vice-versa. Sometime people don't need a CPU upgrade, and an OC might add instability, it might help marginally but usually an OC isn't going to free up too much resources globally, it's specific games where that will be of most benefit.
Also the RAM requirement is 'at least 2GB' , 4GB is good, but not the 'at least' minimum for any game currently out there. Which is why 64bit OS still isn't needed, it's nice to have, but I run on XP32 + Vista 32 & W7 64 (and previously Vista 64), and it makes a little difference, but I wouldn't be telling people to go out and buy an OS, especially not right now, only if they want to take advantage of the W7 pre-order is there value in making a move if they KNOW they need it, not just could get minor benefit from it.
Good ideas, but main thing is to find out how the current game plays first, then upgrade as needed for things specifically noted as issues by people who play the game in question.