Ok as an ex instructor pa 38/28 and that heap of crap the c172.
Mix max, throttle closed.
Under no attempt touch the primer if you even look at it walk away for 30mins.
Wind it over when it catches give a ball hair of throttle.
No pumping of the lever.
No fannying about with any other lever.
If the primer is unlocked on a hot engine to require start the engine is fecked.
mixture rich throttle zero with a small advance when it kicks in.
If in doudt call it a **** while turning