What we did was pick out the model we wanted, then I googled the year/model to find out which local dealers were carrying it and asked for their "bottom line out the door" price. Once I had that, I let the other dealers know the best price I was offered. Luckily the one 2 miles away was willing to match the one 100 miles away, and I had 2 others say there was no way they could match that price - they'd only be making $500 on the deal (if that's true or not, I don't know, but the fact they wouldn't come any closer to it, made me feel like I was getting a decent deal!).
Before doing that the dealerships all said they didn't have much room to move on the price, could "maybe" throw in a battery or something. They ended up coming down $2300 from their "can't move on" price.
2015 Starcraft 26BHS
2014 GMC Sierra 1500 SLT