White Hat SEO:
•Guest posting
•To create pages (write articles) for less competitive long tail keywords (with small search frequency)
•Create backlinks by commenting
•Directory subscription (still works if we are talking about white quality directory)
And you need to remember that SEO is about optimisation, so your work is not just backlinking, you need to remember about
•Website structure optimization
•Effective keyword selection for your niche, product and target
•Content optimization (it contains not only text quality but also clearance and formalization)
•Technical optimization (The site should work steadily and rapidly)
•Inbound linking .
And it is necessary to listen to everything that Google recommends, except ranking factors. Google is not interested to say something clearly on this. But they are interested, to make sites more clearly for their robots, and they can determine the relevance of the page clearly.
Grey Hat SEO
Black Hat SEO I would divide into, Grey Hat SEO and Black Hat SEO.
For me it's a big difference.
Grey Hat SEO is something between White Hat SEO and Black Hat SEO with the main idea to stimulate search engines to rank website faster creating backlink profile more agressive.
•The most popular and effective technique now are PBNs.
Black Hat SEO
And Black Hat SEO techniques are
•Hidden Content (the idea is to show for users and robots different content on the same page)
•Creating Doorways or Gateway pages
•Cloaking
•Clickjacking
•Negative SEO (for example: creating a huge amount of bad links for competitors' sites to drop them in ranking)