A good way of preparing:
Buy the Bluebook, take a timed practice test to see how well you do.
Possibly buy a book that'll help with whatever subject you're doing bad in.
Read Silverturtle's Guide (posted on this website)
Read Sparknote's Guide
There's also online videos that could help like Reasonprep on YouTube
Probably want to buy Direct Hits to study vocabulary if you need it
I'm naturally good at critical reading, so I can't help you much here
Just read a lot, practice, and I'm sure many guides on this site can help with CR. Just look at the stickied thread posted on this sub-forum
This is pretty much similar to writing; just use/find resources like YouTube videos, guides on CC, and there's specific books to help with math as well.
Study at whatever pace that'll help you achieve your goal. Most importantly, keep taking practice tests, analyze your mistakes, and repeat!