All chokes used will depend on the range you can expect to shoot. Turkeys are the only of those that I'd recommend using an extra-full on. IC is when you can expect close flushing birds...modified is an all around choke and is usually what I have in my shotguns. The full choke is for long shots of 30-50 yards. Go too open a choke and you won't have a deadly pattern. Go too tight and you'll have a hard time hitting your target.
As for shot sizes...
Pheasant: 4, 5 or 6. I prefer 5. Lead.
Duck: 2, 3, 4. I use 3 or 4, steel.
Rabbit: 5, 6, 7 1/2, 8. I use 6 or 7 1/2, lead.
Turkey: 4, 5, 6. I use 6, lead.
Squirrel: 6, 7 1/2, 8. Any will do, lead.
Canadian Geese: T, BBB, BB, 2. I use BBB or BB, steel.