These link building methods are best avoided. It is possible that we will get initial good results with these methods, but it is more likely that we will eventually be punished from using them.
Many links from unrelated websites
It is acceptable to get some links from unrelated websites, but if we get too many of them, Google will suspect that we perform a manipulation scheme. Naturally, websites should get links from related and relevant sources. Links from unrelated webpages will have much less values than those from relevant sources. If we have too many irrelevant links, we could find ourselves in a huge problem. (Risk level: 6)
Blog comment spam
Comment section in blog is meant as a place where people can share their thoughts and opinions. Spammers often use well-targeted anchor text when they create links for specific websites. Adding link to our website in comment section is acceptable if it is really helpful for users. However, using bots and scripting languages to automatically create links may endanger our link-building efforts. (Risk level: 7)
Guestbook spam
Guestbook may be a rather outdated component to add in our website. However, many websites still have guestbook that are added years ago. Just like comment section, it is a place where visitors can write freely, in this case to introduce themselves. Spamming the guestbook could result in severe degradation in ranks. Again, we should add our link only if it is helpful for readers and they appreciate it. (Risk level: 7)
Too many links from the same C class of our IP block
Websites located in the C class can actually be located in the same network. This may suggest that the SEO professional simply create links from websites that are also under their management. It is something that we need to avoid and search engines will consider these links as both useless and inappropriate. It is possible that a webmaster with website from the same C block genuinely adds our website, but it is not possible to get too many links from the same C class of IP block. (Risk level: 7)
Automated link exchanges
Link exchange activity can be generated through server-side scripting and other methods. Not only link-exchange is an inappropriate way to get links and we could aggravate our mistake by using automatic scripts. These codes could generate large number of links automatically and search engines can be really suspicious. Identifying websites with this of activity is actually quite easy and they will be punished accordingly. This is a certain way of losing our rank and getting de-indexed by a search engine. Link exchanges performed in a massive scale would leave a huge footprint that we can’t hide easily. (Risk level: 9)
Web rings and link farms
Web rings are worst kind of link exchanges and it is an obvious attempt to trade links between websites. This scheme can be detected very easily by search engines. Link farms are webpages or websites filled only with links. Performing these link building methods are like committing a SEO suicide. (Risk level: 10)