any tips for reef diving

Long exhale encourages heart into bradycardia or slow resting rate....so does immersing your face in cold water prior to diving, take your mask off and hang on the surface with just your snorkel in and do your 3 minute breathe up prior to going down....also you can try the Performance Freediving warm up .....best I can remember goes like this....
Pull down your anchor rope to 15 feet, stay there til you feel the urge to breathe, surface ....3 minute breathe up. Then pull down to 30 feet, same thing , wait til you feel the urge to breathe, come up.3 minute breathe up again. Then do a negative.....I.E. passive exhale at the surface and swim or pull down 30 feet.....it will feel a lot deeper as you'll be compressed and feel like you're down at 60+ feet.Stay down 'til you need to breathe(..won't be long! ) and come up....
Most of us are so impatient to get hunting that we go fast and don't relax and it takes about 2 hours of diving before we get our best breathhold. If you can take the time to do this type of warmup you'll achieve your max breathhold times much earlier in your day. Time spent relaxing and breathing at the surface is actually time ''invested'' in your next dive and allows quiet observation of your fellow reef dwellers!

Bones

Once you've done the Bones warm up, have the attitude that you really don't care if you spear that big fish or not and you will probably be able to get much closer to it. Don't be afraid NOT to shoot that fish if you have a less than perfect look at it. There will be other days and other dives. You may find that it will present itself for a better shot. This will prevent the killing of a fish that may tear off due to poor shot placement and give you better a shot/lost fish ratio.
Just try to be another fish on the reef.

It was already mentioned, but I'd like to repeat it. Aspetto, lying quietly on the bottom, works better for me than anything else. Just go down and wait quietly. They really do come to you. Typically the small fish come in first. Wait them out and the big ones will start showing up. Wait even longer and the big ones will come in closer, and hopefully close enough for a shot.
Howard

In hawaii unless we are diving caves typically you just lay on the bottom as still and as quiet as you can. Dusting with sand or sediment brings in alot of fish, also we will take a piece of coral and either scratch the side of your gun or another rock. Uku(green jobfish) Ulua(GT) Porrot fish,and countless others love this sound. brings them right in.

Usually when I spark their attention Ill stop, if they keep comming in line um up. If they turn around scratch a few more times, 9 times out of 10 they will turn back around and come in closer.