Rinse and neutralize with a high pressure rinse to clean.
Seal Grout (Optional - recommended to protect appearance over time).
This tile has been cleaned regularly with vacuuming, swiffers (wet and dry), mopping, and sometimes with a bucket of ammonia and water and a rag on hands and knees. The grout had turned nearly black from buildup over the years.
Close up of the dirty grout.
We apply a cleaning agent, scrub and allow it some time to work. Then the tile is scrubbed by a high temperature, high pressure rinse enclosed in a bonnet with vacuum suction around the perimeter. This allows us to rinse and neutralize the grout and tiles without creating a mess in your home. The floor is dry in minutes. The grout may need to sit overnight before the color is entirely settled.
This is the tile as it is being cleaned. Look at the difference in the color of the grout.
Close up of the dirty grout.
This is the tile as it is being cleaned. Look at the difference in the color of the grout. 
Here is the end result. The tile looks great.
The Grout looks amazing!