I'm happy to be of help. I think RC was one of my relative strengths and therefore I didn't go about my preparations of this segment very systematically.
1. How much time do you spend on reading a passage (whether long or short)??It would depend on the passage. Some I could grasp in 3 minutes while others took as long as 5 minutes (I would imagine). My strategy was to make sure that I understood all sentences in the passage prior to even looking at questions.
2. How much time do you take to read and answer all questions of a passage (whether long or short)??As previously stated, I spend 3-5 minutes reading the passage. After that I use no more than 1 minute on each question.
3. Which approach do you use?? Skipping or notes taking approach??It did not take notes. I think whether or not to take notes depend on your note-technique and memory capacity.
Lastly, my advise would be that you should spent more time on passages that you have a hard time understanding. The time lost on these passages should then be regained in the easier RC's.
Good luck!