Stick with what you know and trained to do, discuss and agree with your buddy any out of air, low on air scenarios before you hit the water, even with people you have dived with before, their set up or yours may have changed since the last dive, happens often, long hose, bungy 2nd around neck, air 2, octo not where it was before, pony bottle [you will see that I hope] etc.
simple, but not done enough if at all.
That includes a snorkel as a new diver [if you are trained with one] , after diving for awhile you will work out what is or not required, dive what you know , learn as you go along, don't change too much too soon.