I'm on Bitminter. With USB Block Erupters. Very easy setup. Theoretic rate however is about double what I'm being paid out in reality but from what I gather, payout is often random to start but will grow with time. Is that true ? How this all works is beyond me at the moment but I'm learning every day.
Payout seems to be based on your last 10 shifts; currently about 20 hours of mining. Your hash numbers should be within 10% of those on the site. Look for hardware errors or high stale count if this is not the case.