How do you get horizontal movement with a rocket jump?

If you want to get vertical height, fire a rocket at the floor. If you want to get horizontal distance, fire a rocket at the wall. Crouch jumping amplifies the effect for both.

If you aim the rocket at about knee level on the wall, you'll give yourself the perfect angle to perform a couple speed pogos to gain even more momentum. Once you have this practiced, you'll be at the enemy's spawn gate in no time.

I usually fire at the wall while crouching. That seems to get me the farthest with a unique rocket launcher. To get around the map, I use a quick flick of my wrist to turn around and fire at the ground behind me as soon as I land.