If you're using wooden skewers, it's a good idea to soak them for at least half an hour to help prevent splintering and burning.
Cut the chicken into fairly small pieces and trim off any fat/gristle. Place it in a medium-to-large bowl.
Add the mustard, honey, garlic, and salt & pepper to a bowl (or just stir it right into the measuring cup you used to measure the mustard in). Stir until smooth. Pour it over the chicken, and give the chicken a stir so it's coated.
Refrigerate the chicken for at least an hour, preferably 2+ hours. If marinating overnight, cover it with plastic wrap.
Once your chicken is done marinating, oil your BBQ/grill's grate and pre-heat it to high. Thread the chicken onto skewers (I had 5 skewers). Pour any extra marinade over them.
Reduce heat to medium-high. Cook the chicken for about 15 minutes total time (or until it's cooked through), turning every few minutes. We used our gas BBQ, cooking the chicken with the lid down.