Roll inverted. If the model requires a lot of down elevator to remain level it''s nose heavy. If the model pitches up it''s tail heavy. The model should requie a very small amount of down elevator to hold level flight when inverted.

Another method.

Roll the model into a nearly vertically banked turn. If the nose drops it''s nose heavy. If the nose rises it''s tail heavy. This presumes you can roll into a steep bank and stay off the the controls for a moment.

Another method:

Pull into a hover. If the model always falls to the belly or the hatch and not to the sides it''s nose heavy.

Another method:

On short approach at lower power settings if the model continues forward nose high without operator input it''s tail heavy. If the plane continues forward nose down and descending quickly it''s nose heavy. If the plane requires a lot of speed to make a stable approach without snapping to one side it''s nose heavy.

Another method:

If the plane requires a lot of up trim for level flight it''s nose heavy. If it requires a lot of down trim it''s tail heavy. The amount of trim and it''s direction is always a good indicator of cg position.

I use all of them together to check the cg. After the cg is established go on to other trim checks. Perform no mixing until the desired cg is established. Same with engine thrust angle modifications. Wait for the cg to be done. Of course you should correct any roll trim issues on the first flight to make the flight safer.