Seek professional training from a certified instructor for your first night dive. Most advanced diver courses include this training or if you are in a rush check with your local dive shop and see if they offer training specifically for night diving.  PADI offers a specialty course for night diving that teaches the standard procedures used by night divers that are important for your safety and convenience.

Be sure that you tell someone of your dive plans, including where you will be diving, who will be with you, what time you expect to be back, when you expect that you will check in once the dive is finished and emergency phone numbers for the local rescue authorities.  This may seem extreme but just like going on a hike it is always best to be sure that others know your plans so if there is an emergency they will know where to start looking for you.

Know the law for where you are diving

Some parks and beaches close after sunset and local fishing laws may change at night so check with a local dive shop or bait store before your dive.   Also, be aware of the parking restrictions in the neighborhood.  The worst thing is to return from a wonderful dive and find an expensive ticket on your vehicle or your vehicle towed.

Don't be late

Plan ahead where you are going to be diving and arrive prior to sunset to give yourself plenty of time to unload and assemble your gear, familiarize yourself with the surroundings, and check your dive site information while there is still enough light.

Start your dive at twilight

One of the most exciting and enjoyable times to start a night dive is at twilight.  During this time you'll experience the reef making its transition from the day shift to the night shift, one of the most exciting periods of activity.

Know the area

Your night dive should be in an area you or your dive buddy is familiar with from one or more day dives.  If it’s the first time you are going to dive the site be sure to arrive earlier in the day and do an exploratory dive so you are familiar with any hidden obstacles.  Be sure you know how to navigate the dive site and how to get back to the boat or the shore area.

Diving at night requires that you use light signals as well as hand signals.  When signaling with your light aim, it towards the seabed where your buddy is looking, not in their face.  The following are common light signals.

Rapid side-to-side movement underwater means, “Attention, look this way.”

Rapid side-to-side movement on the surface means, “Problems come get me.”

A slow large circle means “OK”.  It is the same as the finger and thumb circle.

When you need to use hand signals, shine your light on your hand so your buddy can see it.  If you need both hands then tuck your light under your arm.

Remember that it is important for your buddy to confirm your signal by repeating it, as it is easy to misunderstand in the dark.

Bring a lighted signal device and backup light

Bring several glow sticks to mark your entry site when shore diving.  Locate a fixture that you can attach a glow stick to provide a fixed location for your return to the beach.  Make sure each diver attaches a safety light or glow stick either to his or her tank or snorkel so they can be tracked.

Make sure each diver has their own primary light and always bring a backup light incase your primary light fails.  You only have to have your light go out once without a backup to learn this lesson.

Once you reach the bottom, turn off your light to see how much ambient light there is.  This will also give your eyes a minute to adjust and you will be surprised since with your light off, you'll see more fish and marine life, not fewer.

If you do need light, you’ll want to use the edge of the pool of light to pick out the critters.  This will help to keep them from disappearing and provide you with an enjoyable dive.  Remember to use a minimal amount of light.

Don’t forget to check your batteries and pack extra ones.  The worst experience would be to have your dive light die on you.

Be sure you secure your light to your wrist with a strap, they’re inexpensive and it will keep you from dropping and losing your primary source of light.  Dive lights will drop and dangle from your wrist when you let go of them, so if you need to free up a hand, turn the light off prior to dropping your light. This will ensure that you don't blind other divers or send confusing signals.

If you become separated from your dive buddy, get to the surface safely and shine your light outward while slowly turning in a full circle and looking for your buddy’s light. If you’re diving from a boat, surface and point your light at the boat until you get their attention, then shine it down on your head. Shining your light at the boat will only blind the crew and make you invisible.

Bring snacks and drinks

Be sure to bring snacks and drinks for after your dive. You will have burnt a lot of energy on your dive, so having high-energy snacks, such as energy bars will help satisfy your hunger.  However, you should still drink plenty of water to stay hydrated.

Bring a dry bag