driving test coming up...need sum help

cool, thanx for the tips, hopefully I can round up a bunch more tips from here to help me out on my test.
i got a question:
what is the big mystery about backing up straight? lol, i cannot do it right, i always end up going toward one side. especially when I am looking over my shoulder, one of my friends said its in the way you hold the wheel, but couldnt explain it any further... how do you guys back up in a straight line? (everyone tells me that it is just practice and it will become natural)

thanx again for ur tips so far and I hope i can get many more