Which methods can (and do) you reliably use for multiple niches that generate authoritative links and is scalable based on the amount of time required to obtain a link?
A lot of people want to keep it whitehat or don't have the budget to purchase links.
Let's avoid the junk links, so we'll exclude things like forum signatures, article directories, regular directories, reciprocal linking -- even guest posting for dofollow links is greyhat at best these days, and most big sites either don't accept them anymore or you have to know somebody to get approved.
Examples might be:
The skyscraper technique: Taking a page that has a lot of links and making something better (or more currently updated), then reaching out to sites and asking them to link back to you.
Guest-o-graphics: Infographics where you do manual outreach and offer to write a custom short (200-300) word post in which you include your links.
HARO: Answering questions from journalists in the hope of getting a link back in your quote.
Journalist "stalking": Finding journalists who write on your subject often and getting to know them via commenting, social following, emails, etc. until they know who you are and might be open to a pitch.
Broken link building: Trying to find dead links, replicating the content, and reaching out for a link when you inform the webmaster of their broken current link.
Regular content promotion: Trying to write something cool and emailing sites who have posted similar stuff in the past to see if they'll share it. Might also use Google Alerts to try to make your pitches shortly after something relevant is published.
Doing expert round-ups: Emailing a bunch of experts, asking for a quote on a subject, then hoping they will share the content to promote their own brand. Heard this is getting less effective as more people do it.
Those are examples of ways to get whitehat links. But what have you done that HAS gotten you whitehat links?
Not everything that looks good on paper is effective in the real world. Maybe we can learn from each other's experiences.