When I took my driving test, I was so nervous about being perfect that I messed up a lot of simple things. I paused at a green light, didn't pause at a stop sign. Things like that. I mean, there was this mean-looking registry guy with a uniform and guns sitting in the passenger seat staring at everything I did! I paid too much attention to him and not enough attention to what was going on around me on the road.
Read the driving manual and know the rules of the road. Know how to do things like hand signals, 3-point turns and parralell parking. Be aware of the other drivers on the road. Mostly, though, relax! If you know your stuff, you'll do just fine!