Good stuff already. Here's a few more.
1) Formally educate yourself in your craft.
The amount of time and money wasted doing things over again, or worse, ruining an expensive textile is an all too commmon occurrence. Sure you can pick up a massive amount of information in a resource such as this very one here, but nothing replaces a comprehensive full fledged course on a subject of your intended expertise. Our most popular class is the spotting classes we hold several times a year, but I dare say that more than 80% of the cleaners out there have never taken a spotting class, while the smart ones repeat the class.
2) Read instructions, read owners manuals, and follow their guidance.
Over half of all chemical products are used in some manner contrary to the written instructions, and to the users detriment in a monetary sense. The majority of equipment repairs are in some way related to unfamiliarity with the proper use of the equipment as outlined in the owners manual.
3) Maintain your equipment.
This goes back to reading the owners manual and the scheduled maintenance program outlined in it. New users often ask for information related to the life expectancy of a truckmount or other piece of equipment of high value. Nearly always the answer is a span of time that varies by around 50%! That means telling a guy that his $25,000.00 investment may easily last 8 years, or may only have a usable life of 4 years if he's not willing to protect that equipment by maintaining it.