So you're starting out in Warbands and you've gotten everything filled out, your race picked, and then you come to regions. Regions are simply separate “areas” in the game. In order to a attack a warband in a different region you must undertake the special hawk mission, in addition, all of the regions have advantages/disadvantages. So now, let’s go over the regions.
The Northlands has a +15% bonus to industry. This a nice little bonus if you plan on using a strategy which involves barracks. There are no negatives to being in the Northlands, so don't hesitate to go there if you think the +15% bonus will could help you out.
Mossflower has absolutely no bonuses or negatives. It’s basically neutral a neutral region. If you aren’t running either a barrack based strategy or a hawk strategy, then this is a good place to go. However because of its lack of bonuses it will also tend to have fewer warbands. It’s the default region, however, so there are always going to be some.
Southsward is where you want to go for hawking. It has a +20% bonus to Runes. The Southsward also has a 5% penalty to industry, but this really shouldn't bother a hawker.
Location Hiding Strategy
Location hiding is not a region, but a strategy that involves going to a region that has few people in it, in order to avoid attacks from those unable to prepare hawks. Due to the relative ease of preparing hawks, however, it is generally not very effective. Still, it might keep a few people off your back...