Allow the wood to burn completely to ash, if possible. The embers make some of the best s'mores anyhow, so enjoy!
Pour lots of water on the fire, being sure to drown ALL the embers, not just the red ones. If you're not sure how much water to use, keep going until you hear the hissing stop.
Using a shovel or similar non-flammable item, stir the ashes. Be sure to scrape sticks and logs to remove any embers that might still be attached and hot.
Drown the fire with water again - yes, one more time - to extinguish any embers uncovered during the previous step.
Use your hand to feel whether anything is still hot to the touch. If so, stir, add more water and feel again. Repeat as many times as neccessary.
If you don't have enough water, or any, follow the same procedure using dirt instead. DO NOT bury the fire, as it can continue to burn and could return to the surface.
The creator of this guide has not included tools