If they are ceramic tiles with a glaze over terracotta colour base, normal drills are fine. If they are modern, tough porcelain tiles, you'll need specialist drill bits.
How big is it?. If it's just the glass sticking to a wall, You need to use mirror adhesive from a caulk tube. Other adhesives Will take off the film from back of mirror.
Depending upon size/weight, can hold it in position with duct tape.