The Albright Knot is useful in tying different types of line together (i.e. monofilament to braid) as well as different diameters.
Wind the tag end of the backing around itself and the larger line loop. Take 10-12 winds, keeping them in place with left hand. Pass the backing through the loop so that it comes out on the same side it entered on.
Tighten by pulling on the tag end of the backing while holding both strands of larger line in left hand. Pliers or a hemostat can be used on tag end. With left hand still holding both ends of larger diameter line, pull on standing part of backing. Pull tag end of backing again and standing part one more time. Complete tightening by pulling only on standing parts of larger line and backing.
See an animation of how to tie this knot at Animated Knots.