Clean your terra-cotta clay pot, if necessary, using a clean cloth, baking soda and warm water. Rinse well and allow the pot to dry completely.
Spread old newspaper across the painting surface.
Apply a clear, water-based paint sealer, using a foam paintbrush, to the inside of your clay pot. This polyurethane paint sealer seals the inside of the porous clay, whether you use the pot for plants or as decoration.
Dip a sponge or a foam paintbrush into water-based acrylic paint in your choice of color. Water-based acrylics dry quickly and cover clay pots well. Let the paint dry, then apply a second coat to the pot. Leave the pot to dry for several hours or overnight.
Paint designs or patterns on top your newly painted pot, if desired. You can paint random designs or images or something specific, such as flowers or fruit, using a small art paintbrush. For example, paint three pots of the same size in a bright color to make a set, then paint herbs or herb names for each pot for your kitchen windowsill. Experiment with different color combinations, depending on your intentions for the pot or the colors of the room.
Use a permanent marker to add detail on top of your painted pot. You can write a poem or a saying on your pot, for instance. Make certain the acrylic paint dries completely before using the permanent marker or the ink will bleed.
Polish your newly painted pot by spraying on a clear, water-based paint sealer to the surface. Use two to three coats of sealer to add shine to your pottery. Sealer also keeps your paint and designs protected. Keep your pots looking shiny and new by buffing them when needed, using a dry, soft cloth.