Relax your throat and your chest. All of your inhale should come from the gut/diapragm. Practice taking long, steady lung hits. Start at the fastest speed you can do without tensing up and work your way up in speed as you get more comfortable. The goal is to take the biggest, fastest hits you can without tensing anything up. Don't try to inhale faster than you can without maintaining consistency or minimizing tension. As your control improves, so will your speed and volume. Efficient breathing takes practice.
It should feel like the vapor is pulling itself in as your chest expands. If it feels like you're working for it, then you need to mess with your airflow or work more on controlling your breathing. Make sure you're not inhaling through your nose at all. Sounds self-explanatory, but a lot of people actually do this without realizing it.
Good luck getting specific answers. Cloud chasers think they're like magicians with this shit, man.