Use a Nautical Cleat

Almost every time you stay at a dock, you will have to tie a cleat hitch. It takes practice to tie it properly.

Steps

Recognize that there are three main types of cleats, a cam cleat, a jam cleat, and a clam cleat.
Learn the cam cleat works by opening and holding the rope tightly, while allowing tightening with ease. To use this, simply push the line between the two parts as shown.
Practice the jam cleat works by ridges holding it in place. This one is often used in an outhaul of a sail and must be pulled out to ease or trim and should not be used in lines that are to be eased or trimmed often. Push the line into the cleat as shown.
Study and practice the docking cleat hitch. They are tricky to tie. These hold the boat in place when docked. This hitch is very secure when tied correctly and very easy to untie in an emergency.

Do not trust too much in a cam cleat. They are known to collapse, so if you are to use it, depending on the importance of the line, hold on to for easy manageability.
Go slow so you don't make any mistakes. The last thing you need is for your boat, jet ski, or whatever, to be cruising without you!

Under a lot of pressure, ropes can break. Take care to tie 2+ lines for safety when docking (stern line and bow line) and for larger boats, two spring lines.