'Fuel....air....spark' is my litany.
If the a/c has fuel selectors then I change from whatever it was on to the alternative.
If it has standby/emergency/boost pumps then they go on
If it has manual primer then I ensure it's locked although I keep in the back of my mind that if all else fails then maybe using it might give me some intermittent power.
If it has a mixture control then it gets moved around, usually starting at full rich
If it has carb. heat/alternate air then it gets selected
If it has a throttle (natch...) then that gets moved too.
If it has magnetos then they each get a go at running the engine without the other one.
etc
Pretty much if it has a knob, lever, button, switch or other device that controls any of the three items then it gets moved to an alternative position.