Crate train and persistance. Take her out to go potty often. Praise and treats when she goes potty outside. http://www.ddfl.org/behavior/cratetraining.htm http://www.ddfl.org/behavior/housetraining_puppies.htm
We brought Bella (lab/pit) home at 12 weeks from the shelter. Immediately, we started crate training and after 3 weeks she started letting us know when she needed to go outside. Happily now, at 16 weeks we have been accident free for a week. =)
Welcome! Happy to see a new pit owner! I took Missy out every hour on the hour. As we walked to the door I said "You need to go OUTSIDE?" If she pottied outside, I acted like I had won the lottery! I also gave her a treat. "Good girl, good OUTSIDE!" I kept her in the same room with me. If I couldn't be watching her really well, like keeping an eye on her when she wandered over behind the couch, I would leash her to myself, or to the table leg while I was cooking. We used the crate at night and when we were not home. But I did wake up every hour or so to take her out. If I caught her going in the house, I would grab her up as quickly as possible, and run for the door with her saying, "Outside, outside!" Then when she finished up out there I would do the praise thing.