I can't give you specific advice for S&C as I didn't do it, but I can give you some general pointers on MC:
1) If possible, have a small book of the questions you get wrong and categorize them into modules or topics (that way, you will have an understanding of which area you need to work on); it is quite sad that NESA don't provide worked out solutions to MC and only the answer
2) In general, don't spend too long on MC (they are only worth 1 mark each, and especially for a content heavy subject where you may have essays or short answer questions, you want to prioritize these; losing 1 mark is better than potentially losing 10 on an essay because you didn't have enough time)
3) To prioritize short answer and extended response, you could leave MC till the end, once again, as you should be prioritizing and putting more care into higher mark questions than MC questions