decide which tools u are gonna need.
look at their specs for cfm
buy a compressor which has enough cfm's for your tool...air ratchet uses low cfm, fast tools like a jitterbug sander use really high cfm's
keep in mind that a bigger tank means the compressor cycles on less
The smallest would be a 30 gallon 2 running HP (not peak). I run one of those I was given, but already see the need for a better compressor. I'm thinking 60 gallon 2 stage IR.
One thing I have noticed, the higher quality the air tool, generally the moe efficiently it uses air. My IR impact is much better about air use than my HF knockoff. My HF "professional" ratchet is an air hog, compared to the Chicago Pneumatic Ratchet.
My compressor cannot keep up with a grinder or a cut-off.
Bottom line-get the next size up from what you can afford.
I got this for christmas while I was in highschool and just starting to get serious about working on my Cruisers. It is probably the most serious 110v compressor you will find. I find it to be easily capable of running impacts, cut-offs, paint guns, and the occaisional orbital sander.
i have an ir v-twin in my shop on 90 gal and that baby rocks the twin heads makes for great fill times and the tank size means you can run anything but at $3000 smacks you may want to go a little smaller for a home shop but ir makes some great compressors.
I use a 26 gallon Husky, 5.5 peak hp, 5.1 cfm @ 90psi and 150psi max. I got mine from a trade but I think they're around $300 . I use Master Craft air tools and they run fine http://images.canadiantire.ca/media/images/products/images/CarpentryTools/0587872_450_CC_3aa13.jpg. Using the die grinder requires a bit of patience (bit of an air hog), but really isn't that bad at all. The only air tools that might have a bit of a problem are sanders (get out the old block sander!). Most compressors will also have a sticker showing tools recommended for Continuous Use, Intermittent Use (short powerful bursts) and tools not recommended.