how to find fps when play game?

[babelone]

I use fraps too. Very simple, small program that runs in the background. You can assign a hotkey to trigger the little fps number in a corner of your screen while playing. Many games are playable at 30fps.

[ajsi]

125 fps is the best possibility.

[Ri0T]

Some games feature an in-game FPS counter, which is activated either by typing an game command into the console (~), or by ticking a box in the game's control panel.
but if your game does lacks one, use FRAPS. To find out whether your desired game feature a FPS counter, use www.TweakGuides.com and search for your game, or simply Google.

[Dark Archon]

Some games has inbuilt FPS testers like Half Life 2 or FEAR. So it also depends on the games you're playing I guess, but generally you use FRAPS.