Cutting Tile for Electrical Receptors

Place the tile(s) that will surround the electrical box next to the box and mark for a cut so the tile will expose just the box opening.
Mark the tile for a notch that will allow the receptacle screw through the box threads. The idea here is to have the receptacle wings resting on the face of the tile and be drawn tight to the tile face when tightening the receptacle screw.

Grouting Tips

Mix the grout per the manufacturer's instructions.
Allow the grout to slake or stand for 15 minutes prior to using.
Never use a drill and paddle mixer above 600 rpm or air will be trapped inside the grout.
Moisten the tile face prior to apply the grout without leaving standing water in the joints.
Force as much grout as possible into the joints.