The very common issue I noticed in Link Building is the fear that site can be penalized by Google for unethical link building. But the thing is who will decide the tactics you are following are ethical or not? This is where you need to implement your common sense when building links for your site.
Let’s take it like this- You come across a technique and discuss whether it’s “ethical or unethical”. However, somewhere in your mind you are thinking that implementing this technique can help you to get traffic. Think again and again- if still you feel it can be beneficial for your site, don’t worry about being penalized.
Why am I assuring you? I have a reason. Google is not the only search engine as there are many more in competition. People always talk about Google because it’s a major one but not all-in-all. Being a supreme, Google will never do anything which can down their reputation in the market. But yes, you should care about the quality of work you are doing, not about Google.
For instance 1: You have a site related to SEO services and you exchange link with a game site or adult site which makes no sense for you or your site pointing to sites like this. Then this could be a reason that Google devalue your link.
For instance 2: When people buy links from thematic and quality sites, there is no reason to get penalized. Getting paid links from link broker and non thematic site can’t help you in any way- neither in increasing ranking nor traffic. In such cases also Google can’t give value to your link.
Being penalized for anything is different from being devalued. Google knows it very well that webmaster’s use number of techniques to rank high and there is no certain rule through which a site can get ranked. So they never penalize you until and unless you are doing something bad, illegal, immoral.
Everyone has their own methods and style in which they are comfortable, but not everything works out the way we hope especially in SEO. Sometimes it works, sometimes not. Hence, Without Google’s fear opt the techniques which you feel would really be and experience the result.