Take with you a packet of biccies and get to know the instructers. They (should) be an excellent source of advice, tips, cheap riding kit and may even know of a good bike for sale for when you pass. The more you show them that you're keen, the more they'll teach you - it's bloody easy to pass the test and be a crap rider, but a good instructor will actually teach you something about 'real world' riding. At least that was my experience (though I'm still a crap rider).
I loved it and sometimes I wish I could do it all over again!
Oh yeah: you can improve your balance for the U turn by practicing with a push bike. You may look a bit daft wearing all your gear though!