Let me add to the post, even though you have already bought a compressor.

1. Figure what size tool will do the job for you. Then double the size and you will be happy. IE if you could get away with a 2HP 15 gal tank, buy a 4 HP and 30 gallon tank and you will be happy.
2 When it come to a compressor. DO NOT buy a universal motor if you can help it. Buy the TEFC motor type. If you see a belt driving the compressor your 99% sure its a TEFC electric motor. Why? the universal motors are VERY LOUD. I know I have one.
3. Electric motor HP. Many store list the stall rate HP. Which is usually twice the normal operating HP. A 6 HP sears compressor with a Universal motor is really a 3 HP unit. Check the amps draw of the motor. A good rule of thumb is 8-10 amps for each 1 HP At 110 Volts. Or 4-5 Amp for 220 Volts. So a 6HP TEFC motor should be a 30 amp setup, That lots of amperage. And this is a rough estimate. Not gospel.

Dave

__________________
1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car