I do a combo of these techniques... I stick a pin in the top layer, right in the center of the seam, 1/4" from the edge. Then I line the pin up with the center of the seam in the bottom layer. With my fingernail, I scoot the fabrics out from the pin in all directions, making sure the pin stays straight up and in place. Holding my iron just above the fabric, I give a shot of steam (just work around the pin). This steam helps the bias relax and fall into place. Then I'll put a dab of washable glue in the seam allowance, set it with my iron, remove pin. Give it another shot of steam and sew.