Building authority on your site is the key to success. To do this you need to make sure that you do your homework prior to writing your posts.
Don't believe the first website you see, not everything online is true. A good technique I use when doing research is to find 3 websites or more with the same content to confirm that the information provided is accurate. Credit to @mrmorrow for teaching me this method.
Another key factor in building online authority is spelling and grammar. Small things like leaving out a capital at the start of a sentence can take away credibility from your posts or not putting a space between two words.
I myself don't have a major in English but with computers these days they can correct most typos for you in a basic spell and grammar check. But they are not perfect! Another way to cover yourself is to get a friend to read over your post. Often a fresh set of eyes will pick up things you didn't notice.