Google has distinct guidelines that ever website owner should review before editing their page or buying links on websites. Violate Google’s terms and conditions and you risk having your web site’s rankings drop considerably. Google’s “Webmaster Guidelines” are fair and provide good recommendations on how to improve your site. As Google states, don’t do something that won’t help your visitors, act as though search engines don’t exist. This is good advice for any SEO project. Optimize for your visitor and the search engines will reward you with good rankings because your content is relevant and well thought out.
Read Google guidelines in full.