My rule(that hasn't already been mentioned) is actually pretty basic.
Get a hobby that doesn't involve any of your partners. This is 600x more true if you are not dating more than one person at a time.
If you do not have a hobby(or at least something that keeps you busy), especially when your partner/s are out doing something(or someone) there is a much higher chance that drama will happen.
This is partially true in monogamy but is less important as it is much easier in a monogamous relationship to not do anything that doesn't involve your partner(I've seen it done, many times in fact).