Here are a few tips I always give to my students:

1) Look outside.
2) Look outside.
3) Look outside.

4) Listen to the engine, if it sounds louder - you are descending.
if it sounds quieter - you are climbing.
5) There is no such thing as "over banking tendency" I can explain if you wish, but what this means is - when you are established in the 45 degree bank, the yoke should be pretty much level (not turned in either direction)
If it is not level, you are probably incorrectly using the rudder pedals.

6) Add power rolling in, reduce power rolling out, don't look at the RPM gauge to do this, just listen.

7) Know your tendencies, know what you tend to do incorrectly and make an effort to not do them.

I am over doing this.... so...

To keep it simple, have your instructor cover up the gauges for the whole maneuver once on altitude and airspeed. While doing the maneuver focus on what the plane feels like, sounds like etc. Find the "picture" that holds altitude and the bank and use small corrections to keep that picture. When done correctly its a beautiful maneuver.

Good luck!