http://www.quiltuniversity.com/squaring_up.htm
http://www.youtube.com/watch?v=KPlo79fz6P0
http://naptimequilter.blogspot.com/2...-tutorial.html
these are all different ideas on squaring up quilts.
trimming a tiny bit to square is fine. you don't want to cut into your blocks if they go out to the edges of your quilt. borders are fair game but again, not much off the edges please. quilts mostly are going onto beds, so square isn't so important.