1) Do not like and/or comment on every picture of someone (of the opposite sex) who is clearly TAKEN.2) Do not constantly message them, especially when they don't even reply? Like WTF goes through your head seriously. #stage5clinger
3) When you add someone, and they ignore your request, do not add them again. Aren't you at all embarrassed?
4) When you see 5+ couple pictures, do not ask them if they are single. I would, however, recommend visiting an optometrist.
If you're in a relationship and you're still getting harassed constantly, you should probably check out my post about Social Media Rules in a Relationship .