Here's a tip a surprising number of steeplers don't know: you want to be going DOWN when you clear the barrier. That is, the apex of your jump is before the barrier itself. That way, you'll get a "boost" almost coming down off the barrier. If you feel like you are falling backwards, it's probably because you're too "tall" in the air.
Check this out:
http://www.trackandfieldphoto.com/DisplayNextJpg.php?060818_2004_2938_RLM
See how crunched up he is in the air? And see how he's coming down when he clears the barrier?
http://www.trackandfieldphoto.com/DisplayNextJpg.php?060818_2004_2954_RLM
Also, check this series of photos out:
http://www.trackandfieldphoto.com/DisplayNextJpg.php?080705_2149_4663_RLM
McAdams starts behind Nelson before the barrier, but because he is able to get down FASTER than Nelson, he pulls up even with him!