How to vaule my game's with keys

See prices at

tf2outpost.com
dispenser.tf
steamtrades.com

While they're heavily frowned upon for purchases (for various reasons which you can read elsewhere), grey markets are a great source for prices, since the sellers there continually adjust them to meet the demand.

I used to just compare with the current trading prices on the Trades section of this site. You can search for the game you have, and see what people have recently offered/bought for in TF2/CS keys.

to be fair i still havent figured out how the whole pricing works .

Its pretty much depending on how much demands there is for a game i guess .

I usually just check the trade section here ... and see what ppl are asking for the game and cut 10% and sell it for that much , or add 10% and try to buy for that much .

I giveaway almost all spare keys i get tho , so im not really a trading expert :p