Summarize the following:
The figure eight knot has a firm, non-slip loop at the end. It is one of the strongest knots there is and ideal for mooring boats. Measure 24 inches (61 cm) from the end of the rope, then wrap the rope into a loop. The tail needs to cross in front of the rest of the rope. Hold the loop in your non-dominant hand. Use your other hand to wrap the tail end of the rope behind the rest of the rope, just under the loop. Pull the tail end upwards and push it through the loop. Pull upwards on the tail end and downwards on the rest of the rope to tighten the knot. If you have enough rope leftover, you can use it to retrace your knot. Simply weave the tail around the knot, following the rope that's already there. This will make the knot larger. If you want to, you can leave a loop at the bottom to hook onto things.

Summary:
Use a figure eight knot if you need something strong. Make a loop near the end of the rope. Wrap the tail end behind the rest of the rope. Feed the tail end through the loop, then tighten. Use the end of the rope to retrace the knot, if desired.