Knot tying takes practice. There are so many times that a specific knot will help you in the long run. These four knots will cover alot of territory. There are many more out there, but with some practice, these will go along way. Yachtpals has put together the BIG four. Check it out
here. If you have never been to Yachtpals, take a look around. At one time, this was a very popular site with tons of good info.