Does anyone know of any good ways of mastering the CR. I

hm It is hard to explain. I usually inherently figure out the argument. I usually do not go , ok here is the conclusion, here is the evidence etc. It usually just makes sense. But for someone having trouble, I'd have to say read and understand the stem. This is big. Then ask yourself questions. For assumption questions you cannot stray far from the argument at all. If the answer choices mention a fact or nouns not associated with the argument at all, I eliminate them. It may be a twist, a similar type of word, something that is mentioned in the stem, but not, so eliminate it. If the stem talks about fuel efficiency, you do not need to talk about fuel cost in the answer choice.

If true questions, look for answer choices that do appear far from the argument but are not. Usually gives scenarios that would strengthen or weaken argument, IF TRUE. Now read through each answer. A LOT might make sense but you need to find the one that gives a scenario that talks to the stem. Think, if this scenario happened, how would it affect what is stated in the question? Ask that question for each answer choice, and MAKE SURE not to lose sight of the stem.

CR on GMAT is airtight. That is what makes it sweet. I really wouldn't practice CR other than official material like LSAT and OFF GUIDE questions. You will just drive yourself nuts because a lot of other questions leave open airleaks.

Once again the above is my strategies. Not sure if they apply in every case, but they work for me.