Ceramic pots are popular vessels for potted plants because they are attractive and widely available. In addition, if the plant is watered regularly, the pot itself will retain moisture and stay relatively cool, providing the best conditions for the soil. Some potted plants do well in very damp environments and are not conducive to the growth of mold, so drain holes are unnecessary. Most plants, however, require sufficient drainage to grow properly and stay healthy for a longer period of time. It is possible to create a drain hole in a ceramic pot with a minimum of specialized tools.
Mark the location of the drain hole with a pencil. It is helpful to mark both the center of the hole, as well as the desired diameter. The diameter of the hole depends upon the diameter of the bottom of the pot, to avoid breakage. The diameter of the drain hole should be about 1/8th the diameter of the pot's bottom surface. For example, if the bottom of the pot measures 8 inches across, the drain hole should be about 1 inch across.
Soak the pot with water if it is unfinished, making sure the clay is saturated. This softens the clay very slightly, and makes it less likely to shatter or splinter. Towel-dry the outer surface only. If the ceramic is glazed, put a few layers of masking tape over the very center of where the hole will be. The tape will keep the drill bit from slipping.
Brace the pot upside-down on the work surface using clamps, and test to be sure the pot will not move. If the pot moves during drilling, the vibration of the drill can cause it to break.
Gouge a small indentation in the very center of the drain hole using a Phillips head screwdriver in a twisting motion with moderate pressure. This will serve as a starter point for the drill bit.
Drill a hole through the gouged area using a very small (no larger than 3/32 inch) masonry bit. Work slowly, and avoid applying too much pressure to the drill. Allow the bit to slowly grind away the clay until the tip punches through the surface.
Drill through the first hole using a slightly larger masonry bit, again working carefully. Keep the drill bit perpendicular to the surface of the pot.
Repeat the drilling process, using a slightly larger bit each time. The goal is to gradually grind away the sides of the previous hole until the desired diameter is reached.
Sand the completed hole lightly to remove any chips and shards. A small piece of sandpaper wrapped around a wooden dowel can be helpful in sanding the interior of the hole.