Originally Posted by
FBinNY
Mount the right crank and tighten it normally and check for play where it's nearest the chainstay. You want to continue to tighten until there's zero detectable play.
When you think you've go it, mount the left arm and test for play by tapping or flexing the left arm and looking or feeling for a reaction in the right one. There shouldn't be any.
This is what I do, although I do have to say in my opinion (and the opinion of the united bicycle institute) is that bearings should be adjusted "as smooth and possible with no play" so too tight over too loose.