The triple surgeons knot is probably one of the easiest knots to connect your tippet to your leader. Its also quite strong. While not quite 100%, it will do the trick. And when you are out on the water, sometimes you want to tie up your rig quickly, to keep yourself on the water longer.
Difficulty: Easy
Time: Fast
Strength: Medium
Usefulness: Attaching two pieces of monofilament or flourocarbon.
Check out the video from the link below.
http://www.mcflyangler.com/triple-surgeons-knot