This task is fairly similar to the strengthen and weaken tasks, in that you should approach all three by analyzing the key points of evidence and positively identifying the conclusion. Rather than trying to find new evidence that affects the argument, however, you should be able to prephrase the type of evidence that you're looking for in a helps to evaluate question. Similar to a fails to consider assumption task, you're trying to find information that is needed in order to judge the argument; whereas in an assumption task that gap will be necessary or sufficient for the argument to be drawn, in a helps to evaluate task, you'll be picking out the piece of evidence that is merely relevant to the argument.
While that sounds easy enough, this task is often coupled with multiple points of view stimuli--he says then she says style--or with mathematical relationships like in the example from the October 1996 free Sample PrepTests. As with all LSAT question types, the distractors can be appealing and/or confusing if you don't know what you're looking for. The key is to stay within the scope of the argument, as the answer choice will have to be immediately relevant to the evidence, bridge, and/or conclusion.
Below is the frequency that this task has been asked on modern LSATs and the percentage change in frequency from pre-2007 LSATs. It averages only 0.4% of the points on a modern LSAT, and so you can reasonably expect to not have a helps to evaluate question on your LSAT.
on LSATs since 2007
|0.4% of LR|
(0 per LSAT, range 0-1)
|-2.1% growth from pre-2007|
Helps to evaluate is one of the few tasks that has all but dissapeared from the modern LSAT. While you may not get a point for practicing it explicitly, the skill of evaluating evidence is highly regarded on the LSAT. Just because you don't get a point on it doesn't mean that it won't help you on other similar tasks, including the point dense strengthen and weaken tasks.