I am looking for good back links for my website. But how do I identify that the site that I am trying to get links from is valuable or not?
Look at the PR of the site you want to make exchange link. Also look at the Alexa rating. The domain age is also important.
Look at the quality of the website you will getting the backlink from. Make sure it as an authorative figure (either with good PR, high on search results, or with many backlinks itself), make sure its content is unique and similar to your niche, and your good to go
My criteria for judging a backlink would be no. of outbound links on that page, domain age and PR of that page
.edu and .org links are very desirable for every website or blog owner to be linked from as Google and other SE reward rank for such back links.. Yet, we need to be cautious and note the comments on some of these sites. If I see spam comments, I refrain to post there to keep my valuable link from mingling in. Important also, besides noting the page rank of a site or extension, note if the site allows Google to follow the link. You can see this by installing SEO for Firefox... you can learn more about it on their site.
Use SEO Addon FF to: + check alexa + check PR + check Do follow link Adds on: SearchStatus, SEOforFirefox,SEOquake
A backlink can be considered as a good backlink if it's in anchor text form, not no-follow link, posted in a relevant site and page, and if ever the page has PR.
It depends what your goal is. To increase PR look at the PR of the site and the number of out bound links. To increase traffic look for high traffic sites.
Sometimes you can identify it by checking the PR of the website where you will get the backlinks from.
First of all ANY LINK can help that is my Motto Secondly Quality links would be from Authority Sites ... Quthority sites are not High PR sites but Aged Sites with high RANKINGS and good traffic ...