Your fingers do a pretty good job of measuring the CG. Just measure back from the leading edge of the wing to the point where the plans say to.. usually over the spar, and then draw a straight line parallel to the leading edge close to the fuselage. Then put your fingers on the line and pick it up. Empty tank, of course, with battery, engine, RX, and servo's in place. If it tends to move toward the tail, then add some stick-on lead weights to the nose as far forward as you can. If it perfectly balances, add one small weight to the nose on each side to make it slightly nose heavy. If it is really nose heavy, then you will have to do something about that like move the battery pack back. If all else fails, then you will have to add some weight to the tail. This is unusual. It usually needs weight in the nose.

As far as lateral balance is concerned, well, some say yes some say no. It's totally up to you. You can check it by having someone help you. Use your finger and pick the plane up by having someone put his/her finger right on the prop nut and someone picking it up right below the rudder at the rear. Use your head. If it goes sligthly to one side or the other, forget it. It won't make a bit of difference until you are way beyond trainers. If it goes heavily to one side or the other, you will have to put some sort of weight on the light side until it gets close to balanced. The same stick on weights will work, but you have to make sure you put them on a solid part of the wing tip and not on a place where the covering is stretched over a rib or something.

I'm sure others will have something to say about this. This is just a guide. Just be sensible about all this. The main concern is CG. If it isn't right (tail heavy), you will not have much longevity with that plane. The lateral balance, on the other hand, is pretty much controllable by the aileron trim.