Drill it out, shoot in an extractor, or if you’re lucky, clamp on some Vise-Grips and hope for the best. But when a drill bit breaks off flush in a hole, there aren’t a lot of options ...
Dull drill bits won't do the best job — or may not ... make sure you secure the bit in such a way that the point is pointed upward — a clamp should work — so that you can sharpen it evenly.