Here are my thoughts. My first strategy is to build great content. But, it's true that no one will link to your content if they don't know about it, so sometimes you need to do other things to get your site noticed.
My second plan of attack is to create linkbait. I've had good success with designing a couple of calculators. The trick is to find something that is REALLY helpful in your niche but that is hard to find elsewhere on the web and to make it easy for people to share on FB and other social sites. These are not always easy to think up! And you need to have the skill to program the calculator (or the cash to hire a programmer). Another type of linkbait I use is to blog about current events, but give people a solution. For example, when the earthquake in Japan happened, a lot of people in my niche were searching for a particular thing in regards to radiation. I wrote an article that answered these questions. I made sure that I researched my keywords and crafted my title so that it ended up attracting a lot of SERP attention even without having backlinks. Because that was a highly searched term for a couple of months it brought traffic and links to my site.
For my informational site the above is all that I do. I will occasionally email a site owner to let them know about some great content that I have produced, but not often. I let my readers promote my content. I make it easy for people to share it in social networks.
I also run a real estate site. It's new and I am currently in the stage of creating a great site so that when I start a link building campaign people will have quality stuff to link to. My first plan of action for my real estate site is to publish a very comprehensive article rating the top ten neighborhoods in my city. I have crunched census data and have my top ten. Then I'm going to write a great article about each of the neighborhoods. Once I have incredible content I will do some press releases, I will personally email local and national newspapers, and I will email people in my niche who will be interested in this type of content. I may eventually add reviews of restaurants, hotels and other businesses within these areas in the hopes of gaining links from those businesses. The possibilities for this one bit of linkbait are endless - I could offer badges (with an embedded link back) for the top businesses, I could have a contest for the schools in each area to come up with reasons why their school is best (which would encourage more linking), etc. etc. My brain is so full of ideas that I don't have time to build all of these things!
I may do some manual linkbuilding for the real estate site such as a few quality directories. I will analyze my competitors' backlinks to see if there are any good opportunities for me. But, so far what I have seen in the competitive link tool are low quality directories that likely won't help.
I considered buying some links, but it's looking less and less attractive to me. For a previous site of mine I bought some links from "sponsor pages". The sponsor part was complete bull because you basically paid some money to sponsor a product you've never heard of and you got a link from a high PR page. These links definitely did help my site. And, I can see how it's tempting to go after them. But here's my thought on link buying: I think that Google is getting better and better at detecting paid links. There are some that they will never get such as if I pay my neighbor to write a blog post about my business and include a link. But, for things like sponsor pages and link farms and "buy an article on this page and we'll link back with three keywords", Google's got Phd's working on anti-spam algorithms.
So, I would hate to go through years of building up my business via linkbait and hard work and hours and hours of content production only to find that I get penalized a few years down the road because I bought some paid links. I can't imagine losing first place rankings, and all of the income that goes along with that (especially for our real estate site) because I got penalized.
That's my strategy for you.