Originally Posted by Basil Moss

Don't bother with the tape. Firstly, don't wrench so hard on your bars. If you climb out of the saddle, tip the bike side to side, yes, but don't twist and wrench at it. You are trying to put your energy into going uphill, not your own personal wrestling match with your bike. Secondly, if you are using a modern, four bolt stem, take the end cap off, and remove the bars. Next, put them back in, and tighten the bolts back down evenly, one turn on each, round and round until they are all evenly tightened. This should do the trick. If you are a massive barbarian of a cyclist, with biceps and stuff, consider going to oversize bars.

I also second the thin layer of grease idea. A really heavy grease like Finish Line would be ideal.