Look very closely where the tire and the rim meet and makes sure the tire is seated exactly the same for 360 degrees. Do this on both sides.
I balance my own tires by running the axle through the wheel and putting both ends on boxes. The heavy part goes to the bottom and I add weight to the top. Really easy and works well. You might be able to do this on the bike itself if you remove the disc brakes. I have drum brakes and they drag a teeny bit and a teeny bit is to much.