Quoted from Hougie:1. Flipper Skills
2. Nudging
3. Master important shots
^In that order. The first two far outweigh the third because "where the shots are" varies examples of the same game.
As others have mentioned focus on dead flipper passing. Try playing onenhanded. That's probably the quickest way to master dead passes.
When the ball is going for the slings give the game a nudge forward (toward the back) that will get the ball up away from the outlanes.
I have two degrees in music performance and I still don't love repetition that comes with mastering a skill, I'm too freaking impatient. Firing up a game and only shooting a difficult shot or a specific flipper skill will pay off when you have practiced it enough. I try to dissect the game into manageable chunks and master one thing at a time.
LOTR is quite a game with several things to master. Can you hit the ring on command from both flippers? The Ring, Legolas, and the Aragorn ramps are where I would focus if you haven't mastered those yet.
There are some great tips in this thread and the three shot that Hougie mentioned are very important in LOTR. Just to piggyback on that, I would also watch videos to see what not to shoot for. That is, certain shots aren't worth the risk and certain shots are better with a less obvious approach, like a backhand or only from a trapped ball. In LOTR, I've found that backhanding the Aragon ramp (or Gimli hole) is a relatively safe shot that is consistently hittable, whereas going at it directly from the left flipper can be a dangerous shot (Palantir!). Also remember, these machines aren't made out of fine china, don't be afraid to push them around a bit. You get tilt warnings for a reason.