What are the factors determine the value of backlinks?

age of domain from which the outbound link is coming from. .edu,.gov being somewhat more powerful domains. anchor text of the link.

Yes. the factors you have mentioned here are correct for gaining back links. Along with those, Quality backlinks can be built by doing social bookmarking, Press Release Distribution, Craigslist submissions. Affiliate programs are also good for getting more visitors (and buyers) and for building quality back links.you can offer to interested sites RSS feeds for free. When the other site publishes your RSS feed, you will get a back link to your site and potentially a lot of visitors, who will come to your site

Relevancy took major role in back link creation. More relevant back link will get more weight than others.

Creating links in your related website. And as long as it is done properly and not in a spamming type

1 - Find the PageRank of each site/page linking to your competitor website.
2 – Find the Anchor Text used in each backlink to your competitor.
3 – Find the number of external links on the same page.
4 – Find the total links on the page
5 – Find the Effective Link Value of the Backlinks
6 – Find out if its a valuable domain listed on DMOZ and Yahoo like directories
7 – Find the exact domain age of the site where the backlink comes from
8 – Find the Page Title of the backlinks page
9 – Alexa Rank of the website linking to you
10 – Domain IP and Region