You will always have more than one goal when it comes to social media and if you don't then you should. Certain posts attract certain things so you should post with your goals in mind. Within your marketing plan you would know what services you want to push at certain times and when you might have quiet spells. You goals might change throughout the year or change focus slightly. Seasonally it would change as in the run up to the holidays you would want to be pushing waxes and pedicures, party season might be spray tans and blowdries etc.
If your goal is conversion, showing behind the scene pictures, up close pictures, candid pictures of a product, customer photos will help to convert a browser to a buyer. Reassuring them that other people have bought and showing them some content they haven't seen before. You caption should be in line with your goal.
If you want to get your followers interacting with you (which in turn creates new followers) then post something that invokes a reaction. Ask a question or an opinion. Get them to tag their friends.
If you’re wanting to create a brand image, most of these pictures cross over with the creating followers and conversion images. You might just want to be slightly more relaxed about the captions/wordy content.
A good mix of all 3 types of posts create a fully rounded social media strategy covering all bases. No one wants to see continuous sales posts or continuous standard white background product shots. They want to fall in love with a brand and find out things they wouldn’t have otherwise.
Define your Goals through your Marketing Plan
Interact with your customers
Find your audience
Always have your goal in mind