"Teh" is now a word because the internet and countless instances of typing without auto-correct has made it so. The "rules" change with time. And guess what else? There aren't actually all that many rules in academic writing that apply across all disciplines. 

ORLY, you say? Well, almost RLY. 

In addition to reminding you of the golden rule ("don't take credit for ideas or written material that somebody else produced/published"), I'll give you some basic guidelines for behaviors you should avoid or embrace that will be useful for most of your academic career as an undergraduate writer. You should, of course, always read the instructions provided for any specific writing assignment and discuss matters of form, style, and content with your professors before you submit written work in fulfillment of it.