Another point which you did mention (between the lines: "and updating your backlinks to point to HTTPS URLs") but I actually didn't realize enough is that updating backlinks when your site switches from http to https is very important. Redirecting all http traffic to the https version of your site from the server (301) is necessary, but doesn't solve losing referral data. Only updating backlinks, especially those on httpS-sites, does. I'd like to emphasize that!
On the basis of this article alone, you should be given a Ph.D in internet traffic generation. Absolutely fantastic set of ideas & sources for traffic generation. I had taken a print of this article the first I read it and then took some serious action of some of the ideas that have mentioned here - flickr images, blog commenting, slideshare (this even resulted in some great business leads and closures), sites such as blog engage, blog interact, social media sources such as LinkedIn, forum participation etc. And they have done wonders to my sites. The fact that there are 319 comments here even as I write is testimony to the authenticity of the ideas presented here. Great article which will one day be a classic - if it is not already.
For reasons we’ve already discussed, traffic from bookmarks and dark social is an enormously valuable segment to analyze. These are likely to be some of your most loyal and engaged users, and it’s not uncommon to see a notably higher conversion rate for a clean direct channel compared to the site average. You should make the effort to get to know them.
In other words, businesses have much less visibility into which keywords searchers are using to find them, making it much harder to understand which words and terms are or working -- or not working -- in their search engine optimization. Google said this would only affect about 11% of searches, but the truth of the matter is the number is much greater than that, and is only continuing to increase as Google's user base grows. It's important to keep this curveball in mind when evaluating organic search as a traffic and lead generation source.
The term “organic traffic” is used for referring to the visitors that land on your website as a result of unpaid (“organic”) search results. Organic traffic is the opposite of paid traffic, which defines the visits generated by paid ads. Visitors who are considered organic find your website after using a search engine like Google or Bing, so they are not “referred” by any other website.