Which digital marketing techniques are more useful in 2017?

Lots of techniques e.g- SEO, SMM, email marketing, online reputation management etc.

All Techniques are useful for your Business..
But You want free marketing service then use SEO, Social Media Marketing and Email Marketing otherwise need instant result and traffic go through Paid Advertising like (Google Adwords, Bing Ads) and also Use paid Social Media Marketing advertising (Facebook Ads, Twitter Ads, LinkedIn Ads) service..

Depends on the mode of business.

SEO techniques (on-page & off-page), social media marketing, video marketing, paid search like: (google adwords, bing ads, facebook ads), there are many techniques but i can't remember except little as i mentioned in this comment.

A short video about your products or services...

All techniques are good...............

Search engine optimization technique for free and organic traffic.

In 2017 Native digital marketing techniques is more useful for the websites.