All search engines will have a set of non static guidelines by which they can make money through advertising revenue. Within this there are types of marketing that are seen as unethical or decpetive and these are termed as Black Hat SEO. If you stay within the guidelines you are considered to use White Hat SEO methods. However it is propbably better to trust someone who has extensive knowlege of algorithms or you trust rather than someone who says they are white hat SEO.