Starting with a dead battery...
All the hardcores already know this, but if your power is dead and you have an outboard, just pop off the cowling and use a rope to manually start the engine. There is a toothed ropestarting gear complete with rope notch on just about every make out there, usually the top-most feature once the cover is off. The notch is angled to give you a hint which way, of not arrow marking is present. Put the engine in neutral, wrap the rope and give it a spin!
Saved our butt many times over the years. Sorry if this is obvious, but believe it or not I've had to remind many people over the years about it so I thought what the heck.