I'll admit it. I've been dinged!. Watch out for anyone who asks you for credit information quickly. Watch out for anyone who uses high pressure techniques such as that the offer will be gone soon. Watch out for anyone who tries to belittle you if you don't jump on this "incredible" opportunity. Watch out for anyone who phones you and starts talking to you about these things (they probably got your number from some one who sold it to them). So watch out for any web purchases that ask for your phone number as a condition of fulfilling the sale. I often put the number of a former employer with an automated answering system.
Watch out anyone who quickly 'pressures' you to buy additional products and services so your 'business' can be successful (consulting, managing, goal setting etc).
If you can pay by credit card you have 90 days to get your money back by filing a dispute with the credit card company claiming the vendor didn't promise what they delivered.
I fell for "Fortune Learning systems" . They have since been indicted for fraud under the FTC's operation Empty Promises. Had I done a quick google search while I was on the phone with the scammer, had I asked for a reference, had I used the lines "let me get back to you", I would have avoided the loss.
I was vulnerable at the time, so watch your own feelings and watch out for anyone who promises instant gratification, quick money, the answer to your problems. Also remember that there is a cooling off period of 3 days when you can change your mind. Be sure you get a phone number if you are dealing with someone over the phone. Ask the scammer for references you can call. Of course there won't be any.
Just my 3.5 cents worth.