We've discussed this previously (on the old forum), but since it's been raised a few times, I thought it deserved it's own discussion here.
Do you, as an author, write a set number of words, try to include a particular passage of time, cover a specific event, or do you try to set up a single conflict (whatever it might be) and resolve it by the end of the chapter, regardless of how many words it takes?
When I started, I aimed for 6,000 words (mainly because anything over 10,000 words on SOL typically broke in random places. I've always been careful about making each chapter distinct, with a clear issue/resolution while leaving the overarching conflicts unresolved, but I'm now working on making my chapters shorter (by about 2/3rds), so it leaves me with much shorter chapters.
But I handle chapters the same way I handle books. I divide books based upon their message. Each book/chapter should convey a different message to the reader. In books, it's a life lesson about life, in a chapter, it's something the characters have to overcome, or come to understand. Once I have this 'theme' in mind, I'll base the entire book/chapter around it, reinforcing the idea throughout, and leaving off anything which doesn't address the basic idea.