what i do listen to some of my favorite tracks to kinda get where things should happen. honeslty in the tracks i make there's not much change up just suttle changes on 32 or 64 counts.

another way is to sit back play your track and when you get to a part in your head where you think something should happen, hit stop and change it. it helps to think of that from the dj point of view.

I like jimfish's reply, im a fan of that notion to, cheesy quick additions that just sound good without a purpose don't seem to add up to much on the floor, they do add a bit more to just listening to it on your tapeplayer though.