The best way to prevent scams and other internet frauds is to learn how a scammer works. No matter what age or how intellect a person is, they can fall into a scammers trap. There are many different types of scams on the internet but if you watch out for the signs of a scam or a fraud, you will be in fact preventing yourself from falling into their trap and losing a lot of money.
People from anywhere in the world can set up shop on the internet. You may hear that most of the scammers and a fraudulent person live in certain countries outside the United States, but just because they have a United States address, does not mean they are not trying to pull the wool over your eyes. They have a magnificent website, an about us page, and even testimonials, but just because it is there does not mean that every word is factual. When a person builds a website, it is up to them what information is put on the site and what you will see if you are surfing.
How can you tell if their website is legit and they are really where they say they are before you purchase? The very first thing you should do is to see if they have an address and telephone number listed on the website. If so, call the you can call the number and see if anyone answers and ask several questions to learn if the company is legit. If you only get an answering machine each and every time you call, I would steer clear. Another way to find out who owns the website is to do a whois check. This can be done at most website that offer domain for sale. The information should give you an actual address and telephone number of the person or company that purchased the domain name.
If you are talking about purchasing items online no matter what they may be the number one rule of thumb is never send money over a wire transfer like Western Union. Even if they are only asking that you pay half up front and then the remainder after your merchandise arrives. Once they get the first half of the money you have no type of recourse if they do not send the product that you purchased. Look for other ways to send money such as PayPal; they do have a system in case you do not receive your merchandise to ask for a refund.
Anytime someone wants to use a third party to act as their agent is another give away that something is up. Remember if they are selling something that you know is a deal of lifetime, it is probably a scam.