First, the GMAT is a long tedious test. It would serve you well to become disciplined enough to work in such long tedious conditions. I would sit there and force myself to become focused on tedious material for long periods of time. I don't know what your attention span is at the moment, but no matter what it is, it would reward you exponentially if you can do one boring activity for several hours because thats exactly what the test is.
What I did was incentivize the work by making it competitive. I'm competitive by nature and love to win. So I found a group of people that I know are studying for the test also and we came up with a plan. We'd all study and work together on practice material over the internet and then on certain days we would take a certain practice test and report our scores to each other over dinner. The person that got the highest score didn't have to pay. The others would split the bill.
The lesson here is that you have to find a way to enjoy your studying. Create an incentive to want to get home, sit down and study and feel good for doing really well on your practice material. Also the group is good because if you can explain how to solve a problem to someone, them you're most likely going to remember how to do that sort of problem if you see a similar one in the future.
This is a long, tedious and difficult process if you're not used to it, but if you practice enough you will become good at it.
I am just getting done with the CR Bible. What I did to help learn the material in this book is read it a chapter at a time. Once I got done I would call a friend or family member to discuss what I learned and provide examples. This requires talking to someone who actually cares about logical arguments, but when you find those couple of people they are always willing to talk about it because they are most likely going to be argumentative by nature and will enjoy the discussion. This really helped me hold onto the concepts instead of forgetting everything I just read. Usually we would talk about politics and I would point out the lessons I learned that day in our discussion.
I would definitely read the CR Bible. Its the best resource out there for teaching you the concepts most important to CR questions. It pays off on the RC and CR sections of the test and in general it will make you a clearer thinker.
If you don't have a group to study with, just get on forums like these and post that your looking for someone who is working through the material also that would like a study buddy to hold each other accountable for your progress.
That is all I have for now. If I think anything else needs to be added I'll post more.
I hope this helps.
Thanks,
Jared