Don’t put all your links in “one basket.” Seek backlinks from many sources, domains and of varying types. For example, reciprocal links from highly relevant sites are great, but that should be a small part of your overall “backlink portfolio.”
Your primary focus should be on one-way links – and the most powerful way to get those is through link bait. (This thread has some great ideas for link bait
Despite their loss of luster, directories remain a viable source one-way links. Think DMOZ, Yahoo, Joe Antl; in other words, think human edited
directories with quality guidelines
; it's the reason Google values those links. Look also for niche directories, and look for deep link directories.
Wherever you can, link back to internal pages
rather than to just your home page – from directories or link trades. If you are successful with link bait, your backlinks are likely to be to internal pages rather than your home page, and you want your backlinks to look as organic as possible.
Vary your anchor text. Your anchor text should not always be keyword rich; you should also use your company name or domain name at times. Again, it looks more natural since webmasters linking to you organically are not necessarily inclined to use your keywords in the anchor text.
If you are doing reciprocal linking, ask the other webmaster to consider a mini article exchange. Your users (and theirs) get more valuable information this way, and your links will be ‘contextual’ rather than the Title: Description
format that is clearly a mark of a link trade.
Keep seeking new sources for backlinks; if you haven’t tried article directories, pursue those; if you have newsworthy events or information, write press releases; if you enjoy sharing information, participate in a forum.
Diversity is the key.