I am looking for some ideas on where to start framing walls in my basement.I have started one wall along a floor beam. Then laying out the wall along the exterior wall I found that something isn't square. I assumed the floor beam was a good point to start. I have poured wall. The house is about 5 months old.

Cut and paste this:

Basement Framing Layout, Part 2 Video ? 5min.com (http://www.5min.com/Video/Basement-Framing-Layout-Part-2-120808205)

Rarely is anything in a basement square. Your floor will rise and sink and the walls are not parallel/perpendicular. Build your first wall laying down on the floor using a pressure treated floor plate. Get this wall square and the nail temporary diagonals to keep it square, raise it in place bolting or nailing into the floor and shimming on the top. Once you get your first wall up all other walls must be square. Oparallel, perpendicular to that wall even if it does not follow the foundation wall. That was a nice video, look for video #1 also