Prevention is the best method: Keep your pH, alkalinity & sanitizer in line and only positive things happen. How often to test is based on how many times you use it/week, how many people/use, and how long/use.
When in doubt I suggest testing 2-3x/week if you really want to be on top of things. Adjust as necessary: If your pH is fine, don't do anything. If your sanitizer is low, add more. I'll defer to others on which sanitizer is preferred, as I do not really prefer one over the other: They all have pros/cons.