What types of links hold good value?

Links within your own Web copy tend to have more value than links in your navigation. If a related site links to you
and is also includes your keyword in their Title Tag, the link on that will have more benefit than if the Title of the page is unrelated.

Initially, Google use to devalue links in some Social Media sites like keyword rich links coming to you from Facebook,
but these days they seem to be carrying more value than they use to. Remember that a link within a caption underneath an image, tends to have a little more value too.