Dynamics
Fuel - Air - Spark are required, in the right ratio, at the right time, for combustion to occur.
I think DanH talked about the "sweep" method (Rich to Lean, or Lean to Rich) in order to find that sweet spot.
When the engine is cold, this is pretty easy -- use the Throttle, Mixture, Boost pump to prime the system with fuel, close the throttle and then hit the start button.
When hot, you may or may not have any fuel in the lines between the fuel servo, the distribution spider, and the injectors. I've begun using the residual fuel pressure to "prime" the fuel lines/injectors -- basically open the throttle to full, mixture to full rich, watch the pressure bleed off a bit, then throttle back to high idle, and hit the start button.
Personally, I've never liked the "you need three hands" approach that seems to be practiced by some CFI's (i.e. Throttle Wide Open, Mixture Rich, Boost Pump On, Start Button, wait for a blade to catch, throttle closed, mixture lean, yaddah yaddah -- [juggle chainsaws here])...