I modified Karan's script to follow only profiles that match a certain keywords to follow only relevant accounts. Please see https://medium.com/marketing-102/how-i-grew-from-300-to-5k-followers-in-just-3-weeks-2436528da845#.75mau0pj9 for details

targeted-auto-follow.js

a = setInterval(function () {
  window.scrollTo(0,document.body.scrollHeight);

  $(".ProfileCard-userFields").each( function() {

    if($(this).find('.ProfileCard-bio').text().match(new RegExp("google|twitter|airbnb|entrepreneur|founder|tech|growthhacking|hacking|official|consultant|analytics|ecom|startup|ceo|ux|seo|ecommerce|growth"), "g") !== null )
    {
      $(this).parent().find('.not-following .user-actions-follow-button.js-follow-btn').click();
    }
  } );

}, 1000);