If you only learn one knot make it the marlin spike hitch. It's simple to tie and leads you right into 4 other great knots. It's much more useful than the common overhand knot which is the same knot you tie your shoe with. If you don't want to tie a knot, check out my invention here.
Here are the 5 knots you can tie with this basic know-how:
1. Marlin Spike Hitch
2. Noose Knot
3. Oysterman's Stopper Knot (trefroil)
5. Twin Bowline Bend
This is how to tie them from a marlin spike hitch and what you would use them for...
The Marlin Spike Hitch.
With paracord you can only pull around 80 pounds of tension before it starts to hurt your hand. This is where the marlin spike hitch comes in. It's a great way to put a temporary handle into rope. If you have more then one person pulling you can add several handles to the line. These handles could be sections of pipe, tree branches, or a closed pocket knife.
To form this hitch you form a loop in the free end of the cord. Fold the loop over so that you can pull a bight of the standing end through the loop. Thread your marlin spike through the bight you pulled through and pull both ends tight. Watch the video in the intro for a better demo.
A marlin spike hitch story.
While changing a water heater I attached a hand winch to a ceiling stud. Once the heater was hoisted up off the pedestal I had my wife pull on a rope which was tied around the bottom of the heater. This let me lower the heater to the ground while it was angled away from it's niche. The handle on the rope was a hammer which was marlin spike hitched in.