Knots are a fascinating subject, about which an enormous amount has been written. Over the centuries human beings have come up with hundreds - probably thousands - of ways to tie a knot in a piece of rope (or several pieces of rope). If you're really interested in the subject, the place to start learning about it probably is the old classic, The Ashley Book of Knots, by Clifford Ashley.
The truth of the matter, though, despite any witchcraft-like claims to the contrary, is that ship modeling really requires two knots: the reef knot and the clove hitch. A handful of others, such as the bowline, the figure-8, and the slip knot (which is really just a simple variation on the reef knot), may come in handy once in a while, but if you get adept at those two you'll have all you need. And getting adept at both of them will take about ten minutes.
Here's a website, courtesy of a British sailing organization, that provides animated instructions: http://www.tollesburysc.co.uk/Knots/Knots_gallery.htm
The reef knot - known to Boy Scouts and other landlubbers as the square knot - is the knot of choice for the vast majority of modeling applications. The clove hitch has one major use: tying ratlines across shrouds. (If you aren't rigging your own ratlines on your model, you probably won't need the clove hitch.)
Hope that helps. Good luck.
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.