Knot-phobes and total beginners start here - Easy-to-follow animations of two easy knots.

Find a scrap length of string or a spare shoe-lace, and any roundish shaft, eg. a chair leg or door handle.

Clove hitch This is one of the simplest knots, and it forms the basis of others. You can use it to fix our fenders.
Watch the "Clove hitch" animation (courtesy of "Grogg"), practice it, then read on, below.

We usually keep one end of a line under a little tension, and tie the knot with the other end.
In "real life" the tight part of the line usually leads "up" from the load. We call it the "Standing line". The other end is the "free end" with which we tie the knot.
Practice it again!

It is simple to develop the Clove Hitch into a more secure knot.
A Clove Hitch is normally tied around a solid roundish object eg a post, or through the slots in Molly's gunnels.
In some situations, the Clove Hitch is known as "Two Half-hitches", for example if tied around a tensioned line.

Round Turn and Two Half-hitches. A long name, but it develops easliy from the Clove Hitch. Use it as a better fix for our fenders.
Tie it in two stages:-
(1) The Round turn - Simply keep one end of the line under a little tension, and pass the free end of the line once or twice around the shaft. Leave enough free line for stage 2.
(2) Two Half Hitches - Keep a little tension on the "standing end" of the line, and on the round turn. Now think of the standing (tensioned) part of the line as if it were a shaft. Use the free end of the line to tie a Clove Hitch (Two half-Hitches) around the tensioned part. Done!
Watch the animation (courtesy of "Grogg"), practice it, then read the notes beneath the animation.

Intermediate knot-tiers try these three (explained and illustrated by PW)

A quick hitch for Molly's bow mooring line (Round turn & two half-hitches on a bight)
The best hitch for Molly's stern line (The Waterman's, Bargee's, or Lighterman's Hitch)
The Molly-cover-securing knot (is only two half-hitches)

Now the three most useful knots for ordinary boaty use. They will enable you to look quite professional in almost any knotty situation:-
Round-turn-and-two-half-hitches (A simple version of one you aready know! - Very useful for fenders)
Bowline
Reef knot
See the links on the right >>

When you have mastered those, rather like "Buy-One-Get-One-free", you will have already inadvertently learned these!
Half hitch
Clove hitch
Overhand knot

Ready to extend your repertoire?
Go for:-
Figure of eight
Rolling hitch
Sheet bend

In some situations, it is useful to tie knots “on-the-bight”. For example "Round-turn-and-two-half-hitches on the bight".
A bight is just a loop; sometimes a rather long one.
It is a way of using up excess lengths of line, and is useful when the end of the line is not accessible, or when it would take too long to thread it around (such as when securing the bow line at our mooring).

Try this excellent website - Animated Knots - Use it in conjuntion with my list on the left

Some other perspectives of popular knots:-
Two Half hitches
Bowline (pronounced Boh-Lin)
Reef knot

Half hitch
Clove hitch
Overhand

Figure eight
Rolling hitch
Sheet Bend

Simpler illustrations of some of the above

Animated versions of some of the above
Other animated versions of them

Hungry for more?
Loads of knotty links
Want to spend some money?
The knot-tiers bible is “Ashley's book of knots".
On a budget? - Browse through a few library books, or a book shop - Choose any uncomplicated book with clear illustrations and comprehensible instructions.