Please read the following page: http://www.inventnet.com/scam.html

The following list by Robert Lougher of UIA can be used as a guide to verify the credibility of an invention promotion company.
The more red flag warnings a company gives, the more you should approach with extreme caution.
"XX" means we recommend that you should not do business with that company.

XX Company refuses to provide in writing the number of ideas they have represented and how many inventors made more money than they invested.

XX Company refuses to provide in writing the number of ideas that have been sent to them and how many they accepted.

XX Company refuses to provide inventor with at least three clients (preferably in the inventor's own local area) that can verify their credibility.

XX If the Company provides a patent search, Company refuses to provide in writing the number of favorable patent searches vs unfavorable searches.

XX Salesmen apply pressure to send money in right away.

XX Company tells you to fully describe your idea in writing and then tells you to mail this information to yourself and not open the envelope. This ploy is used to give the inventor the false impression that the idea is somehow protected. In fact, it does absolutely nothing.

X Company recommends that a design patent be applied for.

X Company provides a patent search without a patentability opinion.

X You can never directly reach the salesman without leaving a message.
The salesman is most likely working out of his home and is using a phone drop.

XX Company claims to be located in one State but all correspondence are postmarked from another State.
Frauds commonly use fictitious addresses and mail drops to hide their true location.

X Company runs slick ads on Radio, Television and national magazines.

X Company offers a money back guarantee if patent does not issue.

X Company recommends submitting your idea to manufacturers without applying for patent first. Most manufacturers we have talked to, will not consider an idea from the outside unless it is at least patent pending.

* You should never have a company evaluate your invention for a fee, if they are ultimately going to charge you upfront fees to represent that invention. This can easily be a "conflict of interest."
Get a third party evaluation from a recognized agency that will have no further interest in your invention.

* If you are asked to initial and sign a disclosure statement, read it. Do not rely on salesman to explain.
Once you initial and sign, it usually deprives you of any legal recourse if you become a victim of fraudulent practices.
Pay special attention to the companies success rate. This would be actual products brought to the marketplace and the inventor made more money than invested. Licensing agreements without manufacturing or successful marketing are not a sign of success.