Don't use no double negatives. Make each pronoun agree with their antecedents. Join clauses good, like a conjunction should. About them sentence fragments. When dangling, watch your participles.
Verbs has to agree with their subjects.
Just between you and I, case is important too. Don't write run-on sentences they are hard to read. Don't use commas, which aren't necessary. Try to not ever split infinitives. It's important to use apostrophe's correctly.