I think the last one is the most important one. When you make an interesting comment to someones article, they will surely check out your content. If they like it, they'll subscribe. At least that's how I do it.
Oh... and there's also Steemfollower;-)
Yah steemfollower. How effective is steemfollower? Do people you get from steemfollower actually engage with you? And upvote your post regularly?
Ok. I will try it out.