Which coin are you trying to mine? there's lots of them - the sites vary in fees and style of payout methods

You can't trust all sites...some of the newer sites for coins don't fairly pay or pay at all....

The ones i've had goodluck with

http://theblocksfactory.com the fees they charge might be a bit high for some people though

Also really like http://minar.cc and http://smalltimeminer.com/