Bad links are easy to come by, and outgoing as well as inbound links should
be considered carefully to determine whether they are to or from bad neighbourhoods.
Obviously, you have considerably less input over inbound links than outgoing
and search engines do realise that you can’t always help getting a link from
a bad neighbourhood.

Outgoing Links

Your main concentration should be when considering linking out to another
site. If you link to a web page that is considered to be spamming or a bad
neighbourhood then you may be damaging your own SEO efforts. There is no legitimate
reason why you would want to promote a spammy site, with very few notable exceptions,
so search engines view this as a sign that you partake in similar activities.

Controlling Inbound Links

Inbound links are difficult to control, and the only time you really need
to consider it is when directly attempting to garner your pages with inbound
links. FFA, or Free For All, link farms offer no benefit to your link profile
and while a link from one of these sites might be easy to achieve, it’s also
pointless.

Reciprocal Links

Reciprocal links are usually embodied by emails that read something long the
lines of “linking to one another’s site provides both of our sites with a search
engine boost”. The reality, though, is that reciprocal links have become greatly
devalued because search engines recognise that they offer no true measure of
the value of a site, only the ability of a person to negotiate a link back.

Link Worthiness

Links are an important part of SEO, and good links can help to drive traffic
directly to your site too. Never link out to a bad site, and remember that
while reciprocal links were once a heavy weapon to help assist in rankings,
changes to the algorithms have greatly devalued their worth.