Link building tip number 2 is about linking to and from related pages.

Link building to your page - Inbound Links

For your inbound links to be effective, it has to come from relevant pages. If you have a site about dog food, and another site with a web page about insurance links to you, it does not give you much weight. In fact, there might be no weight at all.

But if another website about dog training links to you, then your inbound link will help boost your ranking.

The search engines (specially google) have been successful in determining the quality of inbound links so it is best to get links from related web pages.

Linking to other websites - Outbound links

If you are at the giving end, meaning you are linking to another site. Make sure that the site you are linking to has the same or complementary topic. My experience is that, if you link to a site which is not related to your web site's topic, you either get

a. less visits from search engines
b. less pages indexed by search engines
c. both

I learned that the hard way and lost a lot of indexed pages. I had to find those unrelated links that I made to boost my other sites. After a few weeks, I got back the indexed pages that I lost.