There are a lot of thing things you don't want to do while cleaning tile and grout.
Doing these things will prevent you from doing a good job and might even serve to shorten the life of you grout or be extremely dangerous.
The list is as follows: Do not use more water then you need to.
Grout can be extremely porous.
If you use more water then you need to it get trapped in the grout and even under the tile.
Do not combine ammonia and bleach because you won't like the results, a deadly chlorine gas:( Do not use acids and bases to clean at the same time.
Although both of these type of grout cleaners disinfect, they should never be used at the same time.
Do not use coarse scrubbers if you can do the job with an medium of fine scrubber.
Generally I prefer to use brushes when cleaning the grout.
The wear and tear from a coarse scrubber can were out the tile very quickly.
Do not use a grout cleaner that has had color added to it.
Often this can stain you grout, especially if it is a light color to begin with.
Do not use strong grout cleaners and harsh chemicals unless you feel that they are absolutely necessary.
Overtime harsh chemical can break down and destroy the grout if you are not careful.
Do not forget to use a grout sealer.
Having your grout sealed at lest once or twice every few years can make the grout and tile a lot easier to clean.
A good grout sealer actually makes the grout less porous.
Dirt and grime is reflected off the tile and grout rather then absorbed into it.
This also cuts done on the amount of germs and bacteria you have on your floor or in your bathroom and kitchen.