The biggest jump in my LR score started when I began starring and skipping over any problem that looked like it was going to take a lot of time, then using my remaining time (I try to save 12-15 minutes for the 4-6 starred problems) to really dig into the trickier question types (saving the absolute toughest for last, so if I run out of time, it will be on one I probably wasn't getting anyway). I find that getting bogged down with a tough one every 4 or 5 problems is both distracting and tiring, and probably hurts me on the easy ones in between.
The key to that plan is having a lot of time left to go back, though. That leaves ~1 minute for the easier questions. For that to work, it's really important to know exactly what each question type requires so that you don't need to closely read through every answer. As soon as I see the answer that satisfies the requirement (ie. the first one that weakens), I'll quickly skim through the other answers and move on. This isn't great for some question types where the requirements are vague (Main Point, Point at Issue, etc.) and you really need to read all of the answers, but those types tend to not be so common, and/or are the ones I save for close analysis.
Another big help for me was the "Common Incorrect Answers" sections from the LRB. Usually you'll see two or three of the common curveballs on each question, so knowing what to look for is really helpful. Keep these in mind when drilling so that they become more and more familiar.
Cliffnotes: Know the common incorrect answers (mistaken reversals are extremely common), know the requirements for correct answers on Justify, Strengthen, Weaken, etc., and save time at the end for the extra tough questions. I feel like this is pretty standard advice, but it's worked great for me.