Always be honest, and professional, and don't ever bad mouth other guides or equipment. Good luck!
Make sure you teach the people you are guiding; tell them what you are doing and why you are doing it.
Liability insurance will be important (I have no experience with this, thankfully, but it could save your rear end).
You will want to be able to catch a variety of fish since different seasons and conditions bring different opportunities.
Also, understand that it is a very hard and competitive industry. You also will have to deal with a lot of jerks. You also will have to fish on "bad" days, where you don't feel well or just don't feel like getting up. I hope you do awesome, though