How to improve speed and accuracy in RC

I don't think speed matters. You could read a passage at 450 words/minute twice or at 200 words/minute once as long as you get the gist of it. I have scored as high as 99 percentile in Varc and as low as 35 %ile. so it eventually comes down to choosing the right question to attempt. For inference based questions, i use elimination technique. For main idea question, I read the passage like a story and answer only after I've understood everything. For fact based, I usually go back to the passage and read the required details. Hope this helps.