Watch out for low doorways, so you don't hit your head.
You might want to watch out for him too.
Mom always told me to watch out for those fast talkers.
I'm wearing boots and I know to watch out for snakes.
However, watch out for young men on bicycles who try to snatch purses, handbags or cameras.
Treat the cave biota with respect, watch out for them, and avoid disturbing them.