The overwhelming consensus of most seo consultants today is that one-way, authoritative inbound links appear to be the way to go on Google in terms of increasing one's page rank and search engine rankings for specific keywords.
Here are some Ideas for generating one-way inbound links.
1. Writing and submitting articles on relevant subject matter to content/article directories
2. Writing testimonials for industry specific products/services in exchange for a link back to home page
3. Writing an information ebook on relevant subject matter and offering free distribution (viral marketing technique)
4. Writing and publishing a press release of the company
5. Submitting website to targeted directories (Yahoo, Dmoz, Industry Specific)
6. Participating in online forums/discussion boards that allow a signature that links back to home page
Non-suggested link building ideas
1. Reciprocal links exchange (a thing of the past, no longer weighted heavily by Google)
2. Paid text links/ paid text link ads thru a text ads broker (Risky, not natural and Google may penalize sites for doing this in the future. As an alternative, you may want to locate relevant sites with a high PageRank (PR) of say 4 and up and that have very few outbound links. Contact these sites directly or you could have an SEO firm handle this for you, you may have to pay for a permanent link on their site or you could convince them to link to you for offering them something of value in return.)
3. Link Farms - a group of sites that are setup to link to one another (Google could ban a site for participating in this)
4. Other non-ethical seo, spamming methods that could potentially have one's site banned from Google or other search engines
