I vote for the CR PowerScore Bible also. That thing is amazing! It really helped me out. In the first chapter the book says "If you're running short on time to prep, then read the following sections first:..." I don't remember all the sections, but I did that and read through the
MGMAT SC Guide once and improved by verbal score from V38 to V42 on my GMAT retake. I also practiced RC a bit, but I've never had a problem with RC.
Because I realize you're not asking abot books (althought a book would be the best) here are a few of my own suggestions:
Identify each sentence as a PREMISE or CONCLUSION.
PREMISE - a statement of fact that can be used to support or undermine a position or conclusion.
CONCLUSION - A position taken as a result of information presented in the argument. Some Conclusions can also be used as premises for other conclusions.
Example: Sally is tall. Tall people are good at volleyball. Sally must be good at volleyball. Sally must be on her varsity team.
[This isn't a perfect example.]
"Sally is tall" is a premise. It's just a fact (or presented as a fact in the argument).
"Tall people are good at volleyball." Also a PREMISE
"Sally must be good at volleyball." Key here is "must". That signals a conclusion about Sally which is drawn from her being tall and tall people being good at volleyball.
"Sally must be on her varsity team." This is a leap (I admit, but I didn't take a long time to develop a great question.) It uses "Sally must be good at volleyball." to support the conclusion that she is on her varsity team.