Quite often a real estate agent will reduce their listing commission, if they're also working as your buyer's agent on the other end. I reduce mine on the listing side by 1% and if I sell it myself, I reduce it 2%.
It is customary where I live, for the same agent to represent you in both transactions.
As far as finding an agent, I'd ask friends and relatives for referrals first. I treat those referred to me like gold. I greatly depend on a lot of my business from referrals. I owe it to both the person who referred them, and the person who was referred to me, to be the best I can possibly be. (Not that I'm not, otherwise!)
If you don't know of anyone that can offer a referral, search the agents out who list the most in your area and interview them. See which one you think you'd work the best with. Personalities play a big role; you need to be able to work well with the person that you're entrusting such a huge transaction with.
Remember - just because they brag about being a top producer, doesn't necessarily mean that they're a good agent. Trust your instincts and do your homework and you'll find a great agent, I'm sure.
