Two major factors here 1. PageRank
PageRank is determined by the number and quality of links to a page. Both the quantity and quality of text links are important. Always try to get links from web pages with a PageRank rating of at least four.
Concentrate on getting as many different quality sites as possible to link to one page on your site, usually your home page. Do not spread the links to different pages. This will maximize the PageRank of your main page, plus those of the subpages.
2. Incoming Text Link Keywords
ALWAYS provide text links for linking to your site. Avoid image links.
Google does index image links, but without any text for it to index, it won't help your link popularity rating for your important keywords.
In addition:
- Include the most important keyword phrase in the text link, using the EXACT spelling.
- Do not pluralize the keyword phrase, if people usually search the singular version of the phrase. And vice versa.
- Avoid excess words, where possible.
- The linked to page MUST have the text link keywords in the body of the page, otherwise Google will discount the page.
- Include the text link keywords within the title tag of the linked to page. It is possible for a page without the text link keywords in the title tag to get top rankings. But I have discovered that around 80% of top 10 rankings have the text link keywords in the title tag, so always include it.