English (my score: 33): Study grammar rules. I’m a visual/auditory learner, so I listen to videos on Youtube about grammar rules that I don’t know and take notes at the same time. It may also help to run any previous essays you’ve written through a site like either PaperRater or Grammarly, which not only show you your errors but explain them in pretty nice detail and tell you how to fix them, that way you can focus on rules you frequently mess up on.
Reading (34): Well… read. Practice speed reading and take comprehension tests. Annotate while you read (you can google guides for annotating). Take plenty of old reading tests to get a feel for what kind of key information to look out for.
Math (28): Study key formulas. Take practice tests (that’s usually the key for improving, anyways). Make sure you remember as much as you can from late eighth grade (Pre-Algebra) until junior year (Algebra, Geometry, and Algebra II). There are a couple of Math Analysis/Calculus questions, but unless you’re shooting for a 36, missing those won’t screw you up too much.
Science (26): You guessed it- practice tests. You don’t really need any previous knowledge for the science test except maybe some basic knowledge of biology, physics, and chemistry, but otherwise all will be included in the graphs and passages. Practice tests will help you know where to look for the information and what isn’t important. The science looks the most intimidating out of all the tests, but once you know how to ignore what’s not relevant it’s a lot easier.
My first score was a 28, second time around a 30, 5 months later and with almost no studying. I’m not sure what your current score is or what your goal is so I can’t tell you how realistic it is.