how do you write good essays in college?

You take an expository essay class and grammar class and you practice and get constructive criticisms. You ask profs for help. You read good ones and figure out why they are good. You use correct punctuation, grammar and construction. Read, read, read.

It's not about "writing as many as you can to get used to the real thing". Write it so that someone will want to read it- and won't get bored. Make it personal, but also have a message behind it. It's okay to break outside the box when it comes to grammar rules. Don't worry about writing formally, write PERSONALLY. Don't worry about using contractions, first person (in fact you MUST use first person), or starting sentences with conjunctions (and, but, etc.)

Write like 7-10 a week.