If the wing on your airplane is basically straight (and not swept), and if it is conventional wing first, and not a canard.. you can basically measure the chord of the wing (leading edge to trailing edge), and multiply times 25%. One forth of the way back on the wing. Just about every standard airplane will balance between 25%-30%. If you opt for nose heavy, say 20% back from the leading edge you may need slightly more elevator input. If you move the balance point rearward, you will need a larger bag to put the pieces in. Rearward CG location.. a little at a time, will make a airplane less and less stable. Might be great if you want snap rolls to be more crisp. But if you go too far, the airplane becomes uncontrollable. So if you don't have plans, start with slightly nose heavy, and move it rearward as you become more confident, with good control.

If your model has a lifting tail (top of the horizontal stabilizer is curved, bottom side is flat).. the CG can go to the rear a bit more.