Wear safety glasses, gloves, and a dust mask
Score the grout lines with a utility knife if needed
Use a grout removal tool, oscillating multi-tool, or rotary tool with a grout blade
Work slowly along the grout line to avoid chipping the tile edges
Keep the tool centered in the grout joint
Vacuum or brush away debris as you go
For stubborn grout, apply a grout haze remover or grout softener if appropriate
Remove remaining grout residue with a scraper or carbide tool
Clean the area with a damp sponge after removal
Inspect tiles for chips or damage before regrouting