Crouching while in the air lets you travel higher and further than normal.
Let yourself overheal by a medic before you sticky-jump to minimize the risk of not landing alive.
And lastly, as you also mentioned, the more stickies, the higher and further the jump. You will need to overheal to perform sticky jumps of three.
The technique is simple:
Walk to your sticky, jump over it, and when you are just about to reach peak height, detonate. You should be in front of the sticky to boost yourself forward when you detonate, so jump accordingly.
There is a training weapon called The Sticky Jumper with which you can train jumps, or even just use them in the game to fast travel.
It can't be crafted, you can buy it in the store, though.