Never dive without dive buddy Never, never dive alone. Always dive with a buddy regardless of your past experience, and no matter where you intend to dive. This is the key rule no scuba diver should ever violate. In course of your entire dive keep an eye on your dive buddy making sure nothing goes wrong. Responsible dive buddy will never fail to keep observing you either. In case of distress or emergency dive buddy can be your only hope meaning not more nor less than difference between life and death.
Always perform a pre-dive equipment check with your buddy. Before going underwater, you and the buddy should clearly agree upon the maximum depth of your dive, upon how much of bottom time you estimate to have and volume of the air you must start ascending with. Dive buddies should agree upon hand signals they are going to use for underwater communication.
Discussing dive with your dive buddy you plan your dive, and then you dive your plan.