Ahhhh crow hunting,
Its great fun, and depending on how good or bad a shot you are you can go through a boat load of shells in a couple hours, if you find a good spot.
A friend of mine has made it possible to go out on some near by farm land. These areas always seem to produce more crow. Hunting over a fresh manure spread field is a good idea. You should go in undetected in the morning. And yes full cammo and remaining still until you shoot is a must. Decoys are also a must I think for close range shoots. Its a good idea to have one decoy in a tree as the lookout crow. If you use an owl decoy with crows, crow should be lower then the owl.
Where you set up is important also. Crows will approach your decoys at the height of the trees around you. If you can get into some low growing trees or shrubs this will make your job a bit easier. Also try to set up so that when crows approach they will be flying into the wind. This slows them up a bit. Have fun!