Below, I've compiled a list of techniques I personally know of being utilized in the industry. It is by no means comprehensive, but is one of the most complete lists I'm aware of. I've tried to keep each technique as mutually exclusive as possible.
I would like this list to become definitive, so I propose this;
if you can provide 5 techniques not already covered (at the sole discretion of SEP), we will:
a. incorporate your ideas, and give you proper attribution for all to see
b. send you a $50 gift certificate
and … the person who submits the most new link building techniques by February 1st 2009, that ultimately get incorporated into this document (again, at the sole discretion of SEP), will be awarded $250.
Some of the techniques mentioned in this document are not condoned by SEP or the search engines, but are listed only to add to the comprehensiveness of the document. Only you know your own risk tolerance, and so must make the decision regarding tactics yourself.
Each of the techniques below, assumes a basic knowledge of the use of NoFollow tag, robots.txt exclusions, and the identification of bad neighbourhoods.
The Definitive List of Link Building Techniques:
1. build useful tools, that others will talk about and link to. These may be WordPress plugins (eg. a 301 Redirect Plugin for WordPress), Firefox extensions (eg. Dave Naylor's multi-browser SEO Tool, and 97th Floor's Social Media Plugin), and the like
2. build fun or helpful widgets relevant to your business or industry (ie. mortgage calculators, body mass index calculators, how much is my blog worth, etc.).
3. offer badges
4. offer awards
5. issue online press releases
6. build definitive lists or resources via your blog eg. 75+ Link Building Techniques of 2008
8. reciprocal linking with suppliers, clients, and complementary businesses
9. hold a contest. Sometimes even the smallest of contests can result in large numbers of links
10. guest blog on relevant sites in your industry
Image courtesy SEOResearcher.com
11. submit to quality directories
12. submit your blog postings to search engine friendly social media
13. sponsor an event, or a cause
14. provide testimonials for industry products you use
15. vanity bait others - in your blog, include positive mentions of the blog posts of others, and link freely to their work. Often, they'll feel compelled to acknowledge you
16. comment on the blogs of others in your industry, or those of related sites.
17. send samples of your product to industry bloggers and ask them to try the products. If they like them, they may write about them. Of course the risk is, if they don't like them, they may write about them too.
18. participate in surveys or group projects.
19. write "how to" guides or posts
20. release unique research results
21. be the first to uncover and blog about a significant news story
22. post job postings in colleges and universities
23. offer to speak at a college or university
24. help write curriculum for a college or university
25. provide a bursury or endowment to the school
26. make a financial contribution to your college or university. Often this results in a dofollow link acknowledging the contribution.
27. study your local government site to look for opportunities to get listed (ie. news, directory, etc.)
28. use ppc to drive qualified searchers to your quality content, knowing a % will link.
29. syndicate articles
30. trade articles with other webmasters
31. search for sites with dofollow 'trackbacks' and link to some of their blog posts.
32. carefully select your friends on social media (eg. Digg, Stumbleupon, Delicious). If they work for media (eg. newspapers, magazines, radio stations, etc.) cater the content to their apparent interests. I've had content mentioned on radio shows before (and linked to from the radio's website), merely by knowing to put a 'conspiracy' spin on the science content.
33. internal links are crucial and important. Ensure you use proper navigation structure
34. submit to nofollow social media too, if the content is really good. If it goes hot, it will be seen by large numbers of people potentially, and will typically result in a number of good links.
35. study competitors banklinks via Yahoo Site Explorer, and request backlinks from many of the same sources
36. maintain profiles on RELEVANT social media sites with DoFollow profile pages, and heavily link those pages with other pages from the social media site (ie. lots of friends, lots of activity).
37. buy another domain with links pointing to it, and 301 redirect it
38. always carry a camera, capture interesting photos, and post them to the site and Flickr using Creative Commons licensing (requiring links back to your site).
39. include links in the footers of your RSS, so content scaped from your site contains links back to you.
40. rent some links from companies like Text Link Brokers. Be careful though. Google will penalize both the selling and buying party for paid links.
41. strike a deal to purchase a text link ad on relevant pages of a related site. Best if the link is from within a site's actual content.
42. offer to make a contribution to charities
43. as Aaron Wall and Andy Hagans have suggested from their post 101 Link Building Tips to Market Your Website (points 62 and 63), sue a large company (get the David vs Goliath element working in your favour) or get sued by a company that people hate. Genius!
44. interview industry personalities, and post video and text versions to your blog. Others are always interested in what they have to say, and often will find reason to link to something they've said.
45. speak at industry events, especially if you know they offer dofollow profiles and linkbacks for such speakers.
46. apply for awards. Even if these sites do not link back to your site, news of winning awards can often be good linkable content for local media.
47. join a number of local organizations such as the local Board of Trade. Often, these sites provide dofollow member directory links.
48. offer a discount or free product samples to others who blog about your product.
49. submit your blog to RSS feed directories
50. do something remarkable such as running a marathon or triathlon
51. do something controversial, or to infuriate the industry (eg. say SEO is dying to a group of SEOs … good one Jason Calcanis, ShoeMoney). Most will link to you, not knowing they're helping to further promote the issue
52. create niche sites for specific segments of topics of your industry, and link back to your site
53. create an industry group or panel, complete with its own website. Often competitors will not link directly to you, but they will link to sites that link to you!
54. find pages that link to you that are not in the indexes of search engines, and are not noindexed or blocked by robots.txt, and link to those pages so spiders will follow them and find the links pointing back to your site.
55. buy sponsored reviews
56. there are a number of wiki types sites on the internet, that will provide link backs if you add good quality content to their sites.
57. start a search engine friendly affiliate program
58. provide answers via some 'Answers' type sites, and link to your content on the matter as proof of your answer
59. provide a link (from a specific content piece) to a particular site that you wish to receive a link from, and send them large volumes of traffic. Often, this will be enough to capture their attention, and link back to your post on the subject.
60. attend related conferences and network, network, network. People are camera crazy these days, and will post pictures of most of the people the meet, often complete with links back to your site.
61. develop relationships with local media personalities, such that you are their 'Goto' person when they need information on a given subject.
62. some sites have a "See Us In The Press" page. When you find such sites relating to your industry, write something about them. Often, they'll pick it up and post it to their site … everyone like to show off their cudos.
63. forum commenting
64. search keyword "add url", keyword "add site", and add your site to those sites
65. be a 'top commentator' on search engine friendly blogs offering the plugin
66. submit videos to tv channel websites (thank you for this idea Melanie Nathan) and be sure to include relevant text links.
67. point out errors (spelling, grammatical, coding) on sites where you'd like a link from. Often, thanks is provided in the form of a link.
68. develop a WordPress plugin that automatically generates links back to the author's site from the blog where the plugin is 'plugged in' (this is extremely black hat!!!)
69. list yourself with the BBB (Better Business Bureau) and other local organizations. It should be noted however, that not all BBB sites offer DoFollow links
70. submit the widgets you create to widget directories
71. create customized WordPress themes, complete with properly worded attribution links
72. search for articles, sites, or posts that mention your personal or business name, though do not link to it, and then contact them and ask them to link to your site. This is courtesy of Wiep
73. if your company owns numerous web sites, have the other websites interlink. Again courtesy of Wiep
74. find companies offering the same products or services, except in different countries, regions, or even languages, and approach them to exchange links (Wiep … you're on a roll)
75. create an industry niche directory, and link back to your site
76. hold a blog carnival (courtesy Kari Rippetoe)
77. create profiles on Slideshare and Slideboom and upload your PPT presentations. Add your website link to your profiles.(courtesy Kari Rippetoe)
78. purchase links, but disguise them as AdSense or Affiliate Banners … courtesy Gab Goldenberg @ Link Building.ca
80. create geocities, tripod and aol memberpages accounts so you can give yourself guestbook links … courtesy Gab Goldenberg @ Link Building.ca
81. hunt for dying blogspot sites registered through hotmail addresses, then see about getting the hotmail addresses and taking over the blogs … courtesy Oilman and Gab Goldenberg @ Link Building.ca for bringing my attention to it.
82. Use a hub-finder to find the best links, based on them supporting 2+ competitors’ rankings … courtesy Gab Goldenberg @ Link Building.ca
83. Use keyword combination (e.g. keyword listbuilding) tools to combine the various forms of “add url” or related footprints … courtesy Gab Goldenberg @ Link Building.ca
Please Note: many of these techniques are not condoned by Search Engine People Inc., though have been included in the interest of comprehensiveness.
ps apologies Wiep … this list was already well under way when you posted yours. Besides, I think we've touched on some different aspects.