Believe in what you write.
Writing is like an idea. You get it; spit it out.
Take notes if you get ideas. They sometimes come in interesting places.
Proof-read more than once. Bad grammar and spelling ruins your point.
Watch your 'mouth'. Unprofessional comments ruin an article and your image.
Look at articles you like; and make yours one step better!
When you judge your own work, be honest. Lies won't make you a better writer, but learning from your mistakes will.