I try to avoid running the emery or fiberglass cutoff wheels at high speeds to prevent shattering. The best suggestion that I can give you regarding those, however, is that you WANT a full-face safety shield. For anything other than using those wheels, safety goggles should be fine, but I've personally had too many close calls with the wheels shattering.
If you have the cutting disc at any angle other than perpendicular to the workpiece, it will be much more likely to shatter. Just don't be too aggressive with the discs, and your hands should NEVER be anywhere close to the cutting tool (regardless of what it is).
I prefer to use a set of Craftsman mechanic's gloves, an AOSafety full-face shield, and one of those orange Home Depot aprons you get from their Kids' Workshops.
