If you have been absent from diving for at least a year, ask your local retailer about taking a diving refresher program, and include training in first aid and CPR. Refresher programs are short and simple, but more importantly they reacquaint you with skills such as how to set up your equipment, properly use dive tables and/or dive computer, and increase your confidence in the water.
Make sure you have a dive flag that is easily visible to boaters; stay close to the flag, and be alert for boaters who may not see your "diver down" flag.
Always dive with a buddy - this primary rule of diving makes for a safer experience as well as easier lobster hunting.
Make sure your diving equipment has received recent service (such as visual inspections for tanks and regulator servicing) and is streamlined to make your dives easier, safer and with minimal impact to the surrounding marine environment.
Know where the nearest medical and chamber facilities are and how to get there. Consider obtaining dive insurance before the dive season begins to assist in the event of a dive-related emergency.
Plan your dives to be well within safe time and depth limits and stick to the plan.
File a boating "Float Plan" with family and friends. Like a "flight plan," let someone who is not accompanying you on the dive know where you are going and when to expect your return.