It depends on the story, but I try to make each chapter about one "thing" - so it'll either be one long scene or several shorter scenes that go together. That's in stories with one storyline. In a story like Guilty Roads, where I basically have three different groups of characters in three separate situations, I may have several things happening in the same chapter, but I still try to tie them together somehow, even if it's only through how I transition between them.
I don't worry about length too much; I just let my chapters go as long as they need to go to finish the scene(s). If I do have several shorter scenes in a chapter and notice it getting long compared to the other chapters, I do sometimes restructured it to bump a scene or two into the next chapter. I do like my chapters to be "about" the same length, but I have a few thousand word range that's acceptable to me, so it's not too hard to fit most of them into that range.
Sometimes there's not much you can do, though. One of the stories I've started that I'm keeping to myself for now is the continuation to my Nowie slash, and I'm writing it in first person and alternating between Howie's and Nick's POVs. I wanted to keep it balanced like that from the beginning, but I'm finding that Howie's chapters are a lot longer than Nick's so far because Howie's scenes are the ones setting up the rest of the story, whereas Nick is just kind of waiting in the wings for his moment to become an important part of the story. I don't want to write pointless fluff just to make his parts longer, so I've just kind of accepted that I'm going to have a few short Nick chapters compared to the longer Howie ones in the beginning, but I know it will even out once I get further into it. I'm only on Chapter 4.
