Off-site SEO is therefore all the link building and marketing techniques you employ outside the context of your own website.
These include (but are not limited to):
Link building; back-linking and inbound
Press releases and other media articles that directly reference your website
Any article directory submissions you have made
Competitor analysis
Your social media posts and related marketing
Keyword analysis – the popularity and accuracy of your keywords
Leaving comments and links on other sites, blogs, forums, and videos
Submissions to SEO-friendly directories
Videos placed on sites like YouTube, properly optimized
RSS feeds
AdWords and other paid keyword campaigns
Trackbacks.