Few SEO techniques (link-building) are trending nowadays:
Forum postings
Updating and optimization of content
Directories
Social bookmarking
Social media marketing
Press release submission
Infographic submission etc
The Trending link building techniques are:
Forum Posting
Guest Posting
QnA
Micro Blogging
Keyword Research
Quality Content
Local listings
Image Backlinking
Social Bookmarking
Article Submission
Directory Submission
Infographics
Video Posting