I use Doug's method (throwing two loops over the piling, forming a clove hitch)
if I am tying up for lunch. I also have lines made up with snaps on the ends
for places where you can't get to the top of the piling. Wrap it around, snap
it on the standing part of the line and make it fast to a cleat on your boat..
When you are going you just unsnap the line and you are gone. Your crew can
stow the lines underway.
Another knot I like when I am at the ramp or someplace where I am just tied up
for a ninute is a clove hitch with a bight under the last wrap. Then you can
just pull the bitter end and you are out of there. Handy when you launch alone.
It is not a "walk away and forget it" knot.