A mistake that new trailer music composers often do is to not separate each act of their composition (Intro, Buildup, Climax I, Climax II, Outro) properly. This makes it harder for the potential video editor to disconnect them in case they e.g. only want to license the first climax, or another part in the middle of the track.
As a rule of thumb, you should try to make each break one full bar long. There are several possibilities on doing that. Even if you just have half of a bar break it would be much more valuable for the editor to use your track in their trailer.
I highly recommend using SFX in breaks. One thing you might not know yet, is that your music publisher will usually ask for grouped stems. Grouped stems are all your instrumental tracks exported into groups such as “Brass”, “Strings”, “Choir”, “Perc” and so on. One of those grouped stems will be called “FX – Impacts”, “FX – Riser”, etc. Editors can easily remove the FX stem in this particular case, if that’s needed.
So how do you make a cool break?
You can fill the break by using a riser. You can end a section with a radical audio cut. Perhaps a combination of a whooshhit followed by a sub fall (downer) will do the job, too.
This is where tip #1 comes in handy. Make sure to watch for transition points already used in trailers. They already worked well so why not imitating those using your own sounds?