The easiest way to get started or keep up a regular flow is to like, reshare and mention other people and posts; ask and respond to questions.
Posting about your own work is good – try to blend it in with posts on other topics, too. Use hashtags (putting a # sign in front of one or two of the key words in your post) to reach people and communities who are already looking for information on those topics.
It's OK to blend a bit of personal with a bit of professional, but remember the expectations and sensitivities of people in your professional community.
It's a bit more effort, but pictures will bring your research to life and help your posts to get more views. You can post pictures of things like your team or other visitors at your place of work; your poster at a conference or your best slide from your talk; images from your research or the cover of a book or journal you are published in.
Be clear about what you want people to take away from your post. If you want them to DO something, make it clear and easy (“Visit our project webpage” or "Sign up for our workshop").
Repeat, repeat, repeat – your followers will be in different time zones, and will have a constantly moving waterfall of posts. It is normal to repeat posts to make sure you are being picked up by people who check in at different times of day.