Grout is the finishing touch that sets off your new tile job like a frame on a picture, once your tile is in place and it has dried thoroughly. Work on only one section at a time so you have time to clean up the extra grout before it has a chance to harden. Give yourself about 15 minutes after applying to remove the excess or it will set and become difficult to remove without a good bit of scrubbing.
Mix the dry grout powder and water in a clean bucket. Make enough but not too much as the grout will start setting up. Stir well with a trowel to remove lumps. It should be the consistency of chocolate pudding, but not at all runny. It needs to be able to hold its shape. You could buy grout premixed instead and not worry about this step.
Squeeze excess water out of your sponge and wipe off any grout that is higher than the grout space between your tiles. Rinse your sponge often and keep it damp, but not wet. The point is not to wash off the grout you just applied, just to clean off the excess.