Terra-Cotta and Ceramic
Avoid cracking earthenware by marking your target with tape, then using a masonry bit with a winged tungsten-carbide tip (shown).
Plastic
To drill smoothly through plastic and PVC, use a sharp twist bit made from black oxide (shown). Work slowly to avoid melting the material.
Metal
Opt for a bit made from ultra-durable cobalt steel (shown). For harder metals, first use a center punch to make a dent where you want the hole to be.
Fiberglass
Press the carbide tip of a glass and tile bit (shown) into the pot to keep the bit from walking, then slowly press down with the drill.