What criteria for forum that you seclect to build backlink?

[curaqua]

Hi All,
As you known, A website wants to develop in a large community , in addition to building elements good content then build backlinks from other sites is essential , so when you try to build backlink on someone else's site, what criteria  you should select before deciding to put links pointing to your site ?

1. The website or forum has high -reliability, domain longevity Perennial
2. The website has many participants Visitor, better index
3. The website has many useful articles
4. The website has tail .edu, gov
5. Others

Your opinion are?