Hi!
First of all you have to check your wing/stab and engine incident with a Robart incident meter.
The wing, stab and engine should all be set at zero degrees incident. That's the general setting on most of all airplanes.

When you have flown the plane and know that the C of G is rellativly in the right position , check for nose or tail heaviness by flying fast straight ahead and then do a sharp pylon racing turn (To the left) using just aileron and elevator (as usual). The plane should, with it's wing more or less vertical, hold it's heading without the nose pointing down. You should be able to do a smooth turn without any corrections what so ever.
A nose heavy plane will always dip it's nose slightly in the turn.

Always fly at full throttle when you trim the plane for straight and level flight! Thats the rule!