If you aren't familiar with the 80/20 rule in the business world, it basically means that 80% of your revenue comes from 20% of your clients. Therefore you should focus your efforts on gaining more clients like your top 20%.
In short, spend more time on the things that matter, and less time on the things that don't. It's a rule that you can apply to your career, relationships, diet, and even social media.
80% of your social media posts should contain non-self promoted, entertainment value content. People don't use social media to be sold to. They use it to "socialize". Pretend you're enjoying happy hour with some friends after work. Do you think they want to hear you babble on about how great you are at your job? Of course not!
They instead want to hear about things they can relate to. Stories about your personal life. Ways your experience might help them in their lives. Things that make them laugh. Things that make them cry. They want to know you on a personal level. That's what we do when we "socialize".
There's only one rule you should follow in regards to posting entertaining / non-self promoted content: It should be industry related. Here's some ideas:
People love to be entertained. Let's say you are a dentist. You might post photos of funny animals smiling, or the worlds largest tooth!
Everyone is drawn to things that tug on their heart strings. If you are a restaurant, you might support a cause and post content about world hunger or famine.
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Show how you can help people in their every day lives. If you are an auto-body shop you could post ways to save on gas, seasonal car maintenance tips, or do-it-yourself auto repairs.
Be the go-to person in your industry on related products or services. If you are a landscaper, you can review fertilizers or insecticides.
Keep it personal, yet professional. For example you might post some photos from a company party, or somebody's dog they brought to the office.
The remaining 20% of your social media posts can be self-promoted. Your chance to tout your products or services, and how great you are at them. Even though 1 out of 5 posts can be brand specific, that doesn't mean that you should turn into a car dealer (no offense car dealers).
Be sure to offer incentives for your followers to convert. You might give away something once a week by having a contest, or offer a coupon if they provide you with their email address.