1. Complain to a customer service account of a corporation.
There is nothing that screams 'unprofessional' like a twitter account that is full of rants to Tesco about a mouldy sandwich you bought a week ago, or to your electricity provider about how rude Tom was to you this morning. It's not the time nor place for your business account.
2. Go off on a swear-y rant that isn't relevant to your field.
Now, I'm all one for a swear-y rant, but it has to be relevant. When people are voicing their opinions on something that is happening in their field (i.e. the new instagram changes), then that's great. They're creating a debate. But when it's a 10-tweet rant about how the referee was blatantly on Man City's side, keep that on your personal Facebook.
3. Respond to spam/abuse.
It's not worth replying to the bloke who told you to 'get back in the kitchen', or to the three marriage proposals you got when you posted a selfie. Just ignore, report and block. Yesterday, I did a periscope for the first time in months after a big planning session of what I was going to talk about (a mini coaching session). Within two minutes, a lad thought it would be fun to comment that I was 'as pale as Casper the Ghost and no one gives a shit about what you're saying'. I stopped my trail of thought to read it and it completely blindsided me. Then came marriage proposals, sandwich demands and vulgar comments. I wondered if any of my followers were actually there and listening, lost my place and wrapped the scope up quickly. I naively forgot that anyone can view your scope if your location is on, and I spent a few hours being angry at myself for letting it affect me. Now, I know you can block the idiots when they comment and just carry on being badass.
4. Poach other's followers
Commenting on your competitor's Instagram noting similarities to your work is not cool. For example, 'check out our page, we're similar to this account' or 'love what you're doing, we do the same over on our page!'. You're trying to get in front of their followers and show you can also solve their problems, but you're going around it in the wrong way. Interact with them organically, and get them over to your page in a non-creepy, non-poaching way.
5. Have an automated 'Thanks for following' Direct Message.
If I follow someone and I instantly get a 'Hi! Thanks for the follow. Follow me here, here and here' DM, I unfollow them as quickly as they sent that. You can definitely thank people for following, but don't do it in an intrusive, upfront way. A simple 'Hi, thanks for the follow. Your work is great!' creates a dialogue and shows you're not just wanting something from them.
6. Complain about customers/clients.
We all know what it's like to have an awkward customer, but that's no reason to rant about them on the blogosphere. Not only is it deeply unprofessional, but what if that customer saw it? That won't help the situation. Instead, talk to family and close friends about your troubles, and keep it away from the trackable online world.