Small maps, I take the UAV, Care Package, and Predator. That's a spot-on tactic for smaller maps because the fighting is more intense, and there's a 50/50 chance that you might get something amazing (like the Hercules or Apache), so that's bob on I'd say.
For bigger maps however, I'd say that once you get to a level where you feel comfortable getting big Kill streaks, try the higher ones. Harrier Strike, Stealth Bomber and then Hercules (AC130).
And if you get host (like me!) a lot, and you've played far too much CoD4, and know every nuance of the game, then THIS is the way to get a Nuke:
Harrier Strike (Airstrike and Helicopter in one technically. Make sure a friend has a UAV to activate when you call this, as it'll then absolutely murder the other team!).
Apache (chopper gunner). Forget the AC130 if going for the nuke. It's fun, but it only lasts about 20 seconds. You'll have the chopper gunner for about 45 seconds, and you'll get a lot of kills with it very quickly, leading to you getting the...
Tactical Nuke.
So yeah, that's what I pack on Wasteland and such. Harrier, Chopper Gunner, Nuke. My best friend plays with me all the time, and he gets an excellent feed when it's my host (as he's only down the road), so he uses the same as me almost, except he swaps the Nuke for the EMP. The EMP is the only way you can stop a Tactical Nuke in progress, very handy for when you're getting trounced by the other team!
