Originally Posted by MadQuilter

I use the 1" larger than the finished HST as my guide and trim. So if my finished HST is 4" I start with a 5" square. I draw the sewing lines 1/4" from the center and sew on them, cut down the center and press both sides open. Using this method you do have to trim each HST on all 4 sides but it makes for a nicer square. It also eliminates the need for the perfect scant 1/4" seam.

There is also a wonderful HST Tutorial by Rhonda and she uses a totally different method. It may work for you.
http://www.quiltingboard.com/t-37915-1.htm