Today, as part of Link Week, Google is tackling outbound links. An outgoing link is a link on our site that links to another site. This is a kind of vote that we make for the other site, a kind of accreditation on our part, so it is important to use them with good sense and not to link to sites that the we will not recommend…

The qualities of outgoing links…
Outgoing links have many qualities: they help the visitor and establish your credibility by offering content similar to yours to deepen the subject, giving your sources and showing at the same time the fact that you have done researches. Finally, they allow you to build a relationship with experts related to your field.

… And their faults…
However, they have faults if they are misused: they should not be abused (no more than 100 outgoing links per page), they should not be paid for a link (if a link is sold, it must have the no-follow attribute), finally, do not allow spam in comments.

So have these points in mind for making outgoing links, in most cases, if you make a link with common sense there will be no problem …

Source: Webmaster Central Blog.