Never go alone. Not only does this mean you should not perform an investigation working solo, it also means that when your team heads out, you send them out in teams. You could fall, get bit by a snake, be mistaken for a trespasser or any number of hazards. The buddy system will help keep you safer in these eventualities.

Obey the local laws. Don't trespass, or make a lot of noise during your investigation. Act professionally. This is just common sense
 

Go in with the right frame of mind. Do what you've got to do to walk in there with the greatest confidence and concentration.

Don't get cocky - especially in the early stages. "Pride goeth before the fall." Whether in instances of spiritual or physical danger, cockiness is never a substitute for confidence, knowledge and training.