SAT I basically has three components - Writing, Critical Reading and Maths.
In my opinion, Maths is actually the easiest to tackle, but at the first few try, you will find it a bit difficult and odd.
After many practices (and refering to the explanation of the answers), you will learn to answer it by 'shortcuts'.
Writing component tests your essay-writing skills and grammar. (I think the New SAT is essay-optional...)
You will need to spot grammar errors and things like that.
This is also quite easy with ample practices because the grammar rules they test are always the same, so just make sure you master them. (I used a book called SAT 2400 in 7 steps and found it really helpful as it gave specific exercises on each grammar rule! Not sure if they have new edition for the NEW SAT tho.)
Critical Reading is a BIG problem for me. The questions are not asking for direct answers.
You need to try to guess what the author is thinking and justify to find out the correct answers.
One good tip is to read questions (that specify which line to refer to) and go back to the mentioned line, and read multiple times, instead of reading the whole passage at once because there are almost always parts of the passage that are not important to answer the questions.