Post quality content
Be consistent with posting content on your feed. If your account hasn't seen a new post for over three weeks, you severely lack in the posting department. Your followers want new content all the time, and if you aren't providing it, they might click that unfollow button sooner than later.
Engage and interact with your followers and respond to their comments and DMs to show that you are interested in what they have to say. Your followers want to know that you're a natural person, not just a person hidden behind an Instagram account.
Use relevant hashtags
Use specific hashtags that are targeted to attract your desired audience. For example, if you're a fitness guru that posts your favorite healthy dishes and best workout routines, you might want to use some # fitspo hashtags. Use long-tail hashtags in your posts.
Establish a niche
Many popular influencers often have a color scheme throughout most of their entire Instagram feed that is aesthetically pleasing and corresponds to their overall message. If you edit in Adobe Lightroom or Photoshop, pick one or two filters to use on your images and stick to them. For example, if your feed is meant to spread inspiration and positivity, keep your color scheme bright and airy to attract a following that is looking for some light.
If you feature any person or brand in your post, mention them, and don't forget to tag their account. You can do this in both your posts and stories, as well as your highlights. This not only helps increase your engagement but also can expand your reach.
Be yourself and only promote brands and products that you genuinely love and use in everyday, real life. Your followers can sense when there is a lack of originality, and you aren't 100% tangible with them. People want to follow you for your personality, talent, and creativity. Let your personality shine through your posts, and your followers will take notice.