For me the most accurate and easy way to make half square triangles is to use Thangles papers. I used them for the quilt in my avatar and it was a lifesaver with all those triangles. Saves on fabric too. www.thangles.com
You just cut strips of fabric the width needed, layer them with the paper, and then sew on the sewing lines and cut on the cutting lines. Press while the paper strips are still attached and it will be even less likely to stretch on the bias seam. It really is worth the money to buy them. Anyone else found them helpful?