KEEP THESE THINGS IN MIND WHEN TYING YOUR KNOTS:
Wet your knot. Before you tighten a knot, lubricate it with saliva or by dipping it in the water. This will help the knot slide and sit properly.
Pull knots tight. Tighten knots with a steady, continuous pull. Make sure the knot is tight and secure.
Use nippers. You want to trim the excess material after your knot as close as possible without damaging the knot.