1. Read it out loud when you're done. If it doesn't sound right, change it so that it does.
2. For the love of everything grammatical, please learn how to use apostrophes properly. Especially its/it's, your/you're, and yours. "It's" always means "it is." "You're" always means "you are." "Your's" is not a word.
3. There is no shame in using a spellchecker. (There is often shame in not.)
4. Know your audience. Don't use technical terms if you're writing for non-technical users and don't dumb it down for a technical audience.
5. Be concise. There's no need to prove you can use a dictionary or thesaurus to stretch out a sentence or to try to sound more intelligent than you need to be (it doesn't work anyway).
If you want a friendlier guide to grammar than some of the other books listed in this thread (which you should also consider adding to your reference library), check out Grammar Girl's Quick and Dirty Tips for Better Writing by Mignon Fogarty https://www.amazon.com/Grammar-Girls-Quick-Better-Writing/dp...