For the bay park, and parallel park, my instructor gave me specific tips for the car I was learning in/taking the test in. For instance, he would tell me to line up the door handle with the line on a bay 2 a way from the one I was aiming for (or whatever it was--can't remember now) and then just start turning the wheel immediately. Worked like a treat! Ask your instructor if he can give you any points of reference like this. Just be sure that you will take the test in the car you are learning in!
I had similar points of reference for the reverse around the corner (i.e. when the curb hits a certain point in your mirror start turning the wheel) but in all honesty, they weren't all that helpful for me for that particular maneuver. I just used my mirrors a lot to make sure I was close enough to the kerb, but made sure to do some big sweeping looks all around, as they don't want you to just stare in your side mirror!
As for 3-point-turn, I didn't really have any issues with this one, so didn't have any tricks.
Also, you can adjust your mirrors for the maneuvers, just make sure that you stop and re-adjust them before you continue your test!
Good luck!