...specifically a 1972 Sportster. Is there anything special you need to do to get it started again other than re-fueling?
I've also seen the "wiggle" test where you open the cap, rock the bike back and forth and try to see or hear the gas in the tank.This one would have a reserve switch and no fuel pump, like practically all bikes of its day. In fact, there wouldn't be a fuel gage, so riders usually rely on the odometer or let it run out of gas on purpose and then flip to the reserve. It probably wouldn't have a vacuum petcock, but if it did, you have to put it in the "prime" position for a couple minutes after running out of gas, or it will be very difficult to get it started.
If it's been sitting in the weeds for years, it will probably need a full carburetor rebuild and several of its rubber parts replaced, however.