Knots to learn to tie behind your back:

The Prusik Knot is an excellent knot to use to climb up the mast. It uses no hardware that might fail, it's easy to slip up and down the halyard, and locks under pressure. Using this along with a bosun's chair, safety lines and foot holds (made of strong webbing) is an efficient and safe way to go up the mast without requiring someone to winch you up.