The first two points are perfect.I would like to differ from the third though.You could purchase links from a directory but that has to be via your Google Adsense Account.What I would suggest is that you try forum postings and article submissions.What you could do here is to post the URL of your website on your signature and have it attached to your article.If the page is cached it gets counted as an inbound link.For reciprocal link to be counted as a backlink the page of the website containing a link to your website should be cached.As from the the last update for PR and backlinks that Google made in
February it has made it clear that any link pages containing the term "link" or any alpha numeric characters such as 1.html in their url will not be crawled or cached.So for analysts,web-masters who are looking to have their backlinks increased through reciprocal links better don't upload your page/pages as links.html solely for the reason Google will not crawl it.
Rather something like partner or resource will be better.

There are many way to do Backlinks to your website.
-book marks
-press release
-blogs
-blog comments
-Directory Submission

Good ways.

Another way I know is make useful yet controversial posts (possibility varies from niche to niche), but make sure you are within the legal limits so as not to get sued by anyone if you are throwing dirt on others.

You can build back links by utilizing some proven tactics such as bookmarking, directories, articles and blogs etc