Don't use no double negative. Make each pronoun agree with their antecedent. 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, when they aren't necessary. Try to not ever split infinitives. Its important use apostrophe's correctly.