First and foremost a quality glue is a must. I've been using thin AKA glue lately. The thin Losi glue is also very good.

Most hobbyshops sell tiny tubing made for applying tiny amounts of CA. It's designed to fit in the end of the bottle. I cut off about 3/4 of an inch at a time at an angle, insert the straight end in the glue, and use the angled end to glue the tire. You just tilt the bottle, and a very small stream of glue will leave the end of the tube. I place the tube in the center of the wall of the rim, then hold the glue steady and rotate the tire. As long as you don't linger too long in one spot, you should end up with a minimal amount of glue on just the edge of the rim and the edge of the tire.

Best explanation I can give without showing you.