Big air tank and big air flow.
Check your air tools and find out what their CFM requirements are. Take the highest CFM number and multiply by 1.5. Armed with that number, look for a air compressor that will handle it. Use the "free air " or "usable @ ##psi" as your comparison.
The bigger the tank the longer you will be able to use the airtool without having the compressor kick in.
There are also two types of compressors - lubricated and oil-less. Oil-less usually have a slick cylinder wall and are decent for occasional home stuff. But if you use it alot, you'll have to get the engine rebuilt since that material will eventually wear away.