Most of my friends are people I socialize with regularly. We tend to alternate picking up the check. I can't tell you that across a year someone doesn't pay a bit more than another, but it really does even out.

When it's really necesary to split a check, I call ahead, make sure they do it and remind the waiter when we sit down. Some restaurants don't do it because they don't have to do it and don't need the heartburn. If a restaurant won't do it, either lump it or go somewhere else.