what 's the definition of black hat?

Here is some info for ya

seoglossary.com

Google Webmaster guidelines

There is white hat: abiding totally and fully by the guidelines and best practices

Black hat: trying to trick the search bots to increase rankings
An old black hat trick would be to add tons of keywords the same color as the background of your site.

Grey hat: inbetween white and black hat. Not fully abiding by the guidlines, but not officially considered black hat

Thanks for the clarity Al-Scillitani.
There are a lot of so called internet marketing gurus who sell material to other less experienced internet marketers and home based business startups, that want to get an internet based business going. Unfortunately, because the marketplace is so saturated, competitive, redundant, yet lucrative, many of these so called 'secret, never before revealed techniques' are just black hat techniques that have no lasting, and usually detrimental results.

I will be revealing some of those techniques here:
http://www.gooruze.com/members/joesixpack/blog/

Here, I will save you a lot of trouble...

Red flags:

If they say the word "guaranteed."

If they say that they can get your site ranked within a week or two.

If you ask for sites they have worked on and references from those sites and they cant give any to you.

They dont know the difference between a 301 redirect and a 302 redirect.

They have a "canned" approach and do not want to know about your business.

Must sign a 6+ month contract with no out.

**More info for you. Remember, hiring an seo or ppc person /agency is an investment.  It is important you get the right people the first time
Questions to ask seo

 

Great list!

Those are all true for SEO....

oh...and any website that has about 50 testimonials and looks like a "make money at home" site.

and

There is a lot of internet marketing info being sold online through the long sales letter approach. Typically you buy a pdf for a few 10s of dollars. In the sales letter they offer 'secret' or 'never before revealed' techniques.

Usually it's just the standard stuff rehashed, or blackhat techniques (techniques that'll get you de-listed from the search engines), or they are techniques that theoretically sound like they might work, but in reality have minimal impact, or just attract junk traffic.
(junk traffic is traffic that is usually tricked or deceived into clicking through to your site. This type of traffic will rarely ever convert).

Usually they offer great, no questions asked, moneyback guarantees, but they know that less than 10% ever follow through with a refund. And it massively increases conversion rates offering such a guarantee.
But if you buy, and it's a bunch of rehashed or deceptive bull, get your money back. Please!

Well I guess it's a good thing you are trying to blow the whistle, someone has to do it.