Ethical or which likes Google that's called white hat and black hat Google doesn't prefer..if you use black hat then Google may black listed your websites...
White hat techniques are ethical one - getting proper links to a site. Common link building methods like # Social Bookmarking # Directory Submission # Article Submission # Blog commenting - will consider as white hat techniques if you it properly. Black-hat techniques are unethical one and will give good results at first. But in future, ull get ban on your site. It will give you temporary happiness to you but ull pay for your mistake in future.
Black hat SEO tactics such as spamdexing, attempt to redirect search results to particular target pages in a fashion that is against the search engines' terms of service, whereas white hat methods are generally approved by the search engines. White hats tend to produce results that last a long time, whereas black hats anticipate that their sites may eventually be banned either temporarily or permanently once the search engines discover what they are doing. here is Main Resource : http://en.wikipedia.org/wiki/White_hat