Commenting is one of the most underrated ways to earn on Steemit. I've had comments on some of my post earn between $10 and $50! Only because they took into consideration of the second tip. Not being lazy. But at the same time I've seen 1 sentence comments that earn $.50 to $1. Its not going to make you rich but if you spend enough time on the platform and comment on posts that catch your interest you can build your SP balance gradually. Remember, building your SP is the most important factor with Steemit and we need to build that number by any means necessary, and commenting on posts is one of the easiest ways to do it. I recommend looking under tags that interest you, so when you leave a comment you will have some expertise on subject.