黑料不打烊

I don't know what your school covers in English 3, but a surefire way to get better at English in general is to read. I know the advice is overdone, but that's because it's true. Find a genre of literature you're passionate about and just plow through it. Something about reading is very reciprocal: if you do it enough, you'll find yourself able to write effectively with ease.

Usually precalculus starts with trigonometry and covers imaginary numbers, polynomials, conics, rational functions, parametric functions, and limits. It depends what you mean by preparation... it won't hurt to review basic geometry you've learned (especially trigonometry), as well as graphing more complex functions. I recommend Khan academy or Paul's Online Math Notes. To be honest, I've always thought of precalculus as a preparatory class, not so much something that requires intensive preparation in and of itself.