Well, for one, you must not be standing a mile apart from the kissing target and attempting to use your tongue to bridge the gap.
The best way to fix this is to simply hold the target very close to you. As such, you'll find it easy to almost completely merge your lips with the target's. Then you must use your tongue for its true intended purpose, ie: put it inside the target's mouth and explore/coil with the target's tongue at will. But remember to leave a little space for breathing.