When do you use a scene break and when don't you? Is it a weakness to use them every time you're switching scenes?
Well, I've always thought that a scene break should always be used when switching scenes (unless it's the end of the chapter) - though I'm happy for wiser heads here to correct me. If you're concerned about it though,
@cidetraq, one area to look at might be what you define as a scene. Which may be a slippery area - more art than science - but I think in general terms a scene ends when either switching POV (point of view), moving to a different location, skipping a (significant) passage of time (e.g. picking up the story the following morning), or (and apologies this is a bit nebulous) a shift in tone/emphasis in the narrative that marks the section as different to the previous one. There may be others...
The reason I ask about how you define a scene is I remember when I started writing and was trying to wrap my head around when/where scene breaks should occur, and I think I ended up with way more than I needed. I seem to remember I was breaking scenes every time I skipped a period of time, but it's possible to do this
within a scene in a sentence or two without needing a break. For example, in a journey-type story, you could break the scene and start the next with, "The next morning Bob rose with the dawn and set off on the road again." But this passage of time could also be incorporated into a scene with something like, "The next day followed the same pattern as the previous: rain, and wind, and an empty road. The day after that was just as dull. Then someone stabbed him*."
Just an idea but one thing to look at might be to see if some of your scenes could actually be one scene that just needs something to bridge them together. Having said that, there's a lot of variation from author to author as to how long a scene can be. Some keep them short and snappy, others (Terry Goodkind and Tad Williams spring to mind) can keep a scene going for seven years**.
It's been a while since I read it, but I think Jack Bickham's book,
Scene & Structure, may cover some of this (and even if not, it's still a great book and is definitely worth a read).
*It needed livening up and I just couldn't resist
**Perhaps a slight exaggeration