1) Reply To All Your Comments.  In the example below, Poppie Pack replies to all the comments on her Canva blog:

Poppie replies to all comments and makes contributors ‘welcome’.

Why? So that people will know that their comments are valued and listened to.  As a result, they will be more likely to do so again!

2) Twitter.  Personally reply to your new followers.  Tweet back with a ‘thanks for the follow’ or ‘nice to have you on board’.  This response from your will often illicit a ‘favourite’ or ‘retweet’ which in turn might get you an extra follow.  I find this often works well with millennials.