This Hometalker used DecoArt Curb Appeal Paint and it came out beautifully- check it out:

Make sure to clean pots well with your choice of agents, eco friendly or chemica. Then I used latex spray enamel (soap/water cleanup). Spray both inside and outside especially if pots will sit outside in colder climate. After spraying you can stencil or hand paint a design using any latex or chalk paint. Finally I used a clear acrylic sealer x 3 coats making sure to dry well in between. Mine have lasted 5 years thus far. Good luck and have fun!

Actually, I love this natural look! Spray on a bit of moss spray.... very cool!

I would not recommend using oil based paint on old pots. Oil based paints are wonderful for use on interior walls although they do have volatile compounds that some people are very sensitive to these days. Oil based paints won't adhere to plastics or fired ceramic pots and it won't dry well on concrete or terracotta - what ever the wind blows in will stick to it long before the paint is dried.

You need to use paint suitable for the surface you're planning on painting. There are nifty spray paints that work well for plastic; others are formulated for concrete, etc. This is a case for picking the right materials for the job.

Just clean and use as is. Looks great that way!

Krylon has some great super-adhering paint for just this thing. I've repainted all my flower pots Glossy Black and they look wonderful!

I just picked up some broken clay pots. I have ferns and hostas, and put the broken pieces in front to make it appear they are growing out of the pots.