Back-to-Breast Turns: See the information from the USA Swimming and Masters Swimming rule books below. I also included some terrific footage from both goswim.tv and usaswimming.org, which shows the turn done at race speed and in slow motion. **I LOVE the lane line drill included in one of the usaswimm.org links.
EXCERPTS FROM OFFICIAL RULEBOOKS:
Backstroke to Breaststroke — The swimmer must touch the wall while on the back. Once a legal touch has been made, the swimmer may turn in any manner, but the shoulders must be at or past the vertical toward the breast when the swimmer leaves the wall and the prescribed breaststroke form must be attained prior to the first arm stroke.
Backstroke to Breaststroke - Exact Same