Attack the base of the fire, where the fuel source is. You need to break the fire triangle to stop the reaction, and drowning out oxygen is the easiest way.
Each rated pound of fire extinguisher yields approximately one second of use. They go quickly when you’re fighting any fire, and even small fires fight back. 5lb is the minimum imo, look at any commercial setting where OSHA applies and it’s big 10-20lb tanks generally.
Trainers advise to blow the whole extinguisher even if flames aren’t visible to prevent auto-ignition.
You really, really want a hose on any extinguisher. Invert the extinguisher to get under a car/cabinet/low obstacle and the extinguisher is useless as the pressurized gas escapes, leaving behind the powder/foam/water that actually stops fire.
Piggybacking on this PSA to remind everyone;