Explicitly selling links

There is hardly a web master who hasn't heard that paid links can hurt your rankings but still many web masters don't miss the chance to make a few bucks. If you really want to sell links, you'd better use the specialized link selling services, such as Backlinks.com because they are more discreet. However, have in mind that while some of the paid links networks try to hide the fact that the links are paid, the rest are not that discreet. Also, maybe the worst gaffe you can make is to include phrases in website like “Buy 5 PR links for $10”or any other hint that you are selling links. You can include “Advertise here!” or similar messages and still de facto sell paid links but this is not as explicit as listing your prices for links.

Check if backlinks have a “nofollow” attribute

Link exchanges are still one of the white hat ways to build backlinks but unfortunately, there are many unscrupulous webmasters, who will cheat you. One of the scams is when you pay somebody for a backlink, it suddenly disappears or has the “nofollow” attribute. That is why you should check from time to time if the link is still there and if it doesn't have the “nofollow” attribute.