Tips how to save air

№1 - Buoyancy and selection of weights: achieve mastery in establishing neutral buoyancy by accurately selecting the correct weights you need and making sure that you have the correct trim - that is, the position of the body in the water. The struggle with poorly regulated buoyancy requires a lot of effort; constantly pumping and blowing air out of your compensator and this is how you will quickly use up your air supply.
№2 - Care for your scuba kit: make sure that you regularly check equipment for leaks (for example, wear of the O-rings in the first stage of the regulator is a frequent cause of flowing air bubbles) - and transfer your equipment for regular maintenance.
№3 - Properly adjust your scuba gear: experiment with various settings until your position in the water at rest is as close as possible to the horizontal position.
№4 - Use compact equipment: when taking accessories with you, try to stick to those that are designed for storage in pockets. Reducing the amount of equipment will also help you maintain good streamlining.
№5 - Do not strain yourself: perhaps this is the most important factor - try to minimize stress and anxiety; just enjoy the dive. By reducing the number of tasks that you need to perform underwater, you can seriously reduce air consumption.
№6 - Take your time: making  slow and smooth movements, you keep the frequency of your breathing under control to breathe slowly, deeply and smoothly. 
№7 - Keep warm: The more you freeze, the more energy your body uses to function - and the more air you will consume. Remember that in the water you lose the heat of your body about 20 times faster than in the air, so make sure that you wear the proper thermal protection.

№8 - NO hands!: Do not swim with your hands - use your fins only. Paddling with hands is generally ineffective and only makes you tense, requires more breathing, and spending much more air. (An exception here, of course, can be the situation if the diver has physical limitations that do not allow use of fins).
№9 - Dive more!  the more you dive, the better you handle your equipment, the more comfortable you will feel in the water and, therefore, you can enjoy your dive more