The methods vary based on which social marketing platform/s one needs to focus on depending on the time and resources available. I suggest sticking to LinkedIn and Twitter if you want to grow your professional career. These platforms help to not only share your insights in regards to your professional expertise, but also gives you a forum to connect with other professionals from your industry.
To grow your audience on Twitter, you could start off by following people who are the target demographics your profession caters to. Engage with them through their relevant content and have meaningful professional conversations. To grow you audience on LinkedIn, connect with the target demographics your profession caters to, join relevant LinkedIn groups.
Setup a content mix and a content calendar that has to be followed consistently in terms of what insights you would like to share in regards to your profession and industry.
Good Luck Verna, ping me if you need anything else.