Only people that profit from Black Hat SEO are people who buy a domain, put some affiliate ads/article on the site SEO it to death (literally) and drop the domain when it gets blacklisted by the search engines.
If your client has a site he wants to keep going, this is an extremely poor idea. And if you have a legitimate business in SEO, you don't want to get that reputation.
Point him to one of the many Black Hat forums online and let him do his own dirty work.
I came across this piece of advice in the first part of the Learning Center:"Write to educate your readers on your topic: create content on subjects that you are an expert; don't create content for search engines,...
I think SEO is the important role for our blog and website. I just want to know, How to do my SEO for my website and I need to get some tips and tricks to improve my traffic through Search Engine Optimization.