Go into the challenges fully prepared. Take them as if you will take your GMAT test. Most challenges are of high difficulty and are designed to push you. Keep an attitude of learning. Do not worry if you dont complete the challenges. The idea is to apply all you have got to these problems. Once you look at the your performance and study it , you will learn a lot. In my opinion, if you aspire to have a 48+ score on Quant, working on 10 difficult problems a day is better than working 100 medium difficulty problems.
My suggestion for SC is to participate in the verbal forum. Try to explain why each answer choice in incorrect or why an answer choice is the best amongst the rest. Over time, I am confident that you will start doing better. You will learn a lot from other's opinions and styles of solving SC's.
I am not sure about the other materials you talk about.
Finally, keep your focus on learning rather than how many you get correct. When working through problems in the OG or Kaplan, when you get an answer correct, make sure you have used all the knowledge you have in getting that answer. Do not try to move on until you have convinced yourself of the answer. Guessing and Tricks are good, but should only be tools of last resort. When you are in practice mode, tips and tricks actually end up killing the learning. This is not an easy process.
Of all the things that most test takers ignore, it has to be Discipline. Lets face it. After a hard day's work, I'd rather be sleeping or watching TV or spending time withl family. It can get lonely also. You have cut back on your social life and go back to being a student. Feel free to use the Club to interact, relax , share and discuss any issues. Its important to be amongst people who share a common goal.
Being discipline means also tracking your progress diligently. Also, at the end of a study session, if you cannot write down what you have learned, it was probably not the best use of your time. Practice should lead to improvement. Create a feedback loop so that you KNOW you are making progress. Solving 1000 problems does not mean too much if you did not really learn much from them.
Does not sound like fun , I know. It is also my personal opinion. It may not work for everyone.
Praetorian