Let someone know where you are going and when you plan to return. Alcohol or drugs have no place on any cave trip. Always wear a helmet and shoes with lug soles. Sandals and athletic type shoes are totally inefficient. Be aware of the weather conditions if you are going to cave with an active stream in it.
Some caves tend to flood quickly.
Do not attempt advanced techniques such as vertical work, technical climbing or diving unless you have been properly trained and equipped. Know the limits of your group. Your team is only as strong as the weakest member. Tom Fink squeezing through Any caving beyond the novice stage requires some specialized gear. A good helmet is a necessity.