1. Know the aircraft. You may be surprised otherwise by the type specific questions in the theory paper,
2. As the other poster said be very familiar with all the controls and the various procedures - you may be surprised how much seems to be going on during your first few flights - it will help enormously if you really know where everything is,
3. Make sure you are totally familiar with the power settings - you will obvioulsy be spending a lot of time in the circuit - when you are just going round and round things happen even more quickly and that is not the time to be thinking about when to get the aircraft cleaned up, what power settings to use down wind, base and final, when to take flaps and gear. That familiarity should obvioulsy include the same knowledge for circuit work with one engine in op. Your school should be able to give you that information,
In short committ all that to memory and you will find the flying sooo much easier - remember unless you have a background in fast, complex singles a great deal will seem to be going on and it will seem very easy to get behind the aircraft.
Enjoy. It is a great sense of satisfaction to get your multi and for some reason you always seem to feel you are flying a "serious" machine when you are driving a mulit.