What to use in the bottom of flower pots?

Another flower pot, like the ones that the annuals your planting come in. Washout empty butter tubs to place in the bottom.

I use garden rock in the bottom of my pots for good drainage.

I have used packing peanuts. Then you have to put a layer of landscape cloth over the peanuts so water can drain through and so the dirt will not wash out. Don't use the potato or dissolvable type of packing peanuts.

I use packing peanuts in the bottom half of my planter...you can get Them at local pack and ship store

Styrofoam is also good. I save the foam from packing materials. A large plastic pot or pail upside down also works well.

Large gravel will let the pot drain and is also heavy enough to keep the pot from tipping over.

As others have said, pebbles, river rock, styrofoam peanuts, or cut up styrofoam. You don't need a whole lot, just an inch or so.

Styrofoam peanuts are great, but make sure they aren't the biodegradable type or you'll soon have nothing in the bottom. Pebbles are also good. If you have a broken pot,smash it into smallish pieces and use that in the bottom of your new pot.

I crush up the little thin plastic water bottles, the 1/2 liter size or whatever. You can also cut them up with a scissors. The are benign to the plant's roots and they last forever in the bottom of a pot. It saves on dirt when you have a huge pot and not so much planted in it.