The first one is the tactic — I'm going to use very conversational naming conventions for these — the "I made this thing you will probably use." So this is, in effect, saying not, "Hey, I made this thing. Will you link to it?" but rather, "I made this thing and I can have some confidence that you and people like you, others like you, will probably want to link to it because it fulfills a specific need."
So there's some existing content that you find on the web, you locate the author of that content or the publisher of that content, and you form a connection, usually through social, through email, or through a direct comment on that content. You have an additional resource of some kind that is likely to be included, either in that particular element or in a future element.
This works very well with bloggers. It works well with journalists. It works well with folks who cover data and studies. It works well with folks who are including visuals or tools in their content. As a result, it tends to work well if you can optimize for one of those types of things, like data or visuals or ego-bait. Or supporting evidence works really well. If you have someone who's trying to make an argument with their content and you have evidence that can help support that argument, it will very often be the case that even just a comment can get you included into the primary post, because that person wants to show off what you've got.
It tends not to work very well with commercial content. So that is a drawback to the tactic.