Note from the editor: I am writing this on the go, so I have to make it quick. Might make a longer version if I have time.
Do's:
Post quality content
Be active
Be nice
Upvote things that should be Upvote
Explore Steemit's posts
Basically just guidelines for anything like Reddit.
Dont's
Don't spam content
Don't upvote everything
Don't hate too much on people
Don't just post things without any thought
Don't ask for upvotes just because
Don't forget to have fun posting and reading! :)