Good spelling, grammar, and punctuation.
Spelling : Make sure that all I's in in your writing are capitalized. Also, every letter in the beginning of a sentence.
Grammar : Make sure that your words agree with each other so you don't get a sentence that's a little off. For example : She did go get his own brush at the store right now. The correct way to say this is : She went to go get her own brush at the store right now.
Punctuation : Always end yours sentence with either a period, an exclamation point, or a question mark. Always put commas where you need to pause and take a breathe. Also, include apostrophes when needed. Like words showing more than one : headphones. Some times though, they are not needed : headphones.
Hoped I helped!