4. Being a Pest
There's a reason why companies put "no phone calls" on their job listings. They don't want you calling with "Have you made a decision yet? Have you made a decision yet? Have you made a decision yet?"
The same rule applies to contacting hiring managers via social media. Remember, a connection is a sign of trust, a sign that they're willing to hear from you. It's like someone giving you their phone number and saying, "Call me anytime." If you're given this kind of trust, the last thing you should do is call them anytime.
Similarly, don't ask your contact about your job opening. They haven't forgotten about the search, and if you made a good enough impression, they haven't forgotten about you, either.
This isn't like the pity date you got in high school because you kept mooning after the object of your desire. Being a pest won't get you a pity job; it will get you blacklisted.