While Waste is correct, mostly you need enough chlorine to shock your pool.

If you have lines than can collect water even after you drain them, you'll need pool line antifreeze.

You may need to balance your pH with Borax and Muriatic Acid.

I like to add a quart of PolyQuat 60% just before closing.

But, unless you have a problem to solve, that's it.

Me? It's usually just chlorine (IE bleach) and PolyQuat.