I used to suck w/ the RL (is it called the Eightball in U:T?)- the travel time just threw me totally. This was back in the days of QuakeII. Then I started playing lots of Rocket Arena for QII, where I pretty much dedicated myself to it, and now I'm pretty damn good, if I say so myself. Most of the points listed above (instant fire rockets, aiming for the feet/walls near an opponant, etc.) are excelent points. Splash damage from off the floor and walls will eventually kill as well as anything else.
When using the RL, the SINGLE MOST importantthing to to is predictive fire- that is, look where your target is going and then lead him with the shot. I find if I lead about 1 1/2 times as much as my first instinct says, I get lots more hits for some reason.
I prefer to use the RL at medium range, since it cuts the travel time while keeping me out of the blast radius. HOWEVER, since the U:T RL has ther neat-o lock feature, I've found that I'm using it at longer and longer ranges. Don't count on this too much though, as the rockets don't steer all that much- still lead the target whenever possible to improve your chances.
Bottom line: practice, practice, practice. If you want to get better, always use the RL as much as humanly possible, in all kinds of situations. You'll die a lot at first, but once you start learning it's nuances, you will find there is NO cooler feeling than spinning and launching a rocket at a leaping target, and nailing him in midair... mmmm...flying gibs... sigh. =)
-ImagoX
"If you ever drop your keys in a river of molten lava, let 'em go because, man, they're gone."
-Jack Handey