Not enough listening and whole lot of bragging. Bragging is annoying period and is even more annoying when this is all of you post on your status updates. People really do not care if you were editor-in-chief of XYZ magazine 25 years ago. Even more annoying, is when people self-promote when answering a string of conversations. Tooting your own horn is not going to get you new business and you will most likely be removed from conversation strings/groups.
Not having a plan. Have a plan when it comes to social media and do not spread yourself to thin. Pick forums you want to participate in (i.e. where your customers are) and do this consistently, with a goal in mind. If you are blindly and randomly participating everywhere without a goal in mind, you are going to end up in what I call the social media timesuck vortex. Also, please keep in mind that playing mafia wars all day is not going to drive business and people will question if you actually work.
Airing dirty laundry. Keep your personal drama to yourself. Most people do not want to know if you are having a nervous breakdown, boyfriend drama or the details of your food poisoning case and hospital stay. It kind of provokes the thought that you will not want to work with this person now, or possibly ever. Also, if you are going to publicly bash someone on Facebook, you are going to be the one that ends up looking bad. Keep your dirty laundry in the washing machine where it belongs.
Not responding to customers. O.K. This one absolutely kills me and I am rolling my eyes as I type this. I have personally contacted people saying I need a quote or need to order XYZ product with zero response. I am starting to think there must be a lot of self-made millionaires on Facebook, because I really do not get someone who does not want their business to earn money. Always, always, always, respond to your customers even if they are just sending you a “hello” (referral business – hint, hint). If you cannot respond or fill an order right away, just let them know. No response = no bueno.