........ “interprets a link from page A to page B as a vote, by page A, for page B. Votes cast by pages that are themselves ‘important’ weigh more heavily and help to make other pages ‘important’”.

You want to choose sites with a high PR, are relevant to your site and are willing to give you a link in from their site. Now, one thing to keep in mind is that PageRank numbers are for pages, not entire websites. And the Google algorithm is set up so that the amount of PR a page has to “pass along” to it’s link recipients is the PR of the page divided by the number of outgoing links. So if a website has a PR of 6 on it’s homepage, and has 3 other outgoing links, then they actually have only 2 units of PR to “pass along” to each link. And that’s IF they put you on their homepage, which is not likely. They will probably put you on their links page, and since link pages rarely have a high PR the amount they have to pass along is decreased even more.

You would fare better with several links from smaller, lower PR sites, than a few of the high ranked and often elusive commercial giants. Here’s why, first of all it’s much easier to get them to link to you. Secondly, you can probably get them to put your link on their homepage. Third, they will probably have less outgoing links to share their PR. Fourth, unlike Links pages, their Home page will have a lot of on-topic keywords making it a valuable link for you in the eyes of Google. Fifth, it's usually easy to get them to link to you using your keyword phrase in the links. Incoming links that don't include your keyword phrase don't help you. And sixth, these sites are probably not going to stay small and low ranked forever. As their PR increases, so does yours. Can you see how this would benefit you much more than trying to link to the giants?