1. The 80/20 rule applies to social media.
The 80/20 rule says that 20% of your actions will get you 80% of the results. This is true for all aspects of life but especially social media since it's so much work to put out a lot of posts every day.
2. Posting more = lower engagement
People who post more than ten times a day get 25% less engagement than people who post less than ten times a day.
3. Post at peak hours
People are most active on social media between 9am and 5pm local time, so if you post then, you will have the most chance for engagement.
4. Make sure your posts are under 100 characters or they will be ignored by everyone except your followers and friends.
Since people are always looking for new content to post, if your posts are over 100 characters long then nobody will read them and repost them unless they are really into you or really interested in what you wrote.
If you use hashtags on Instagram and other platforms that allow hashtags, then your post will appear in searches for those hashtags so people can discover you that way.
6. Use influencers as co-posters (and vice versa)
Use an influencer to co-post with on Facebook or Twitter but also ask them if they want to do a "collaboration" with you where you both promote each other's products on social media. This is one of the best ways to build relationships very quickly.
7. Use email newsletters as co-posts on social media (and vice versa)
You can write an email newsletter about something completely unrelated to your business and include links to products related to whatever topic is discussed in the newsletter. You can also do this with other people's newsletters (but never copy-and-paste their entire newsletter). Co-posting like this is one of the best ways I've found to build an audience fast since it hits two audiences at once (your newsletter readers AND your followers on social media).
8. Ask questions
People love answering questions
you can answer their question right after they answer yours so it looks like a conversation rather than a question + answer + question + answer etc
I do this all the time on Twitter and it works great
People love it when celebrities respond directly to them like this even if it's just "Hi!" Or "Thanks!"
It makes them feel special even if it's just for a second before moving onto the next follower interaction opportunity
See @jamesaltucher for great examples of how he does this well and often gets tens of thousands of likes per tweet when he does this well (which he often does)
9. Don't forget about messengers
Messenger bots have huge potential but many businesses don't know how to use them yet so sometimes messenger bots can be an easy way for businesses without websites or ecommerce stores to start getting sales right away via Messenger, WhatsApp, WeChat, etc
But make sure there is some sort of incentive (like free shipping) otherwise people won't order from you via these channels because they think they won't get their stuff fast enough if there isn't free shipping involved somehow