Determine if you really have a need for a product. Sure, the infomercials make it seem like not having a self straining spaghetti pot is ruining your life. Mute the TV for a second if you are thinking "ohh that happens to me all the time." These commercials try to pressure you & they are aired late at night when people are tired & not sleeping well. Don't believe it when they say it's for a limited time only. Have you ever actually seen one of these things sell out?
Don't be pressured. You usually have to call to get all of the details from the infomercial. Instead, look up user reviews so you can make your decision in a relaxed manner. This way you won't have sales people pressuring you, & you won't feel like you are wasting anyone's time.
Look at shipping. Most infomercials double your offer if you call within a limited amount of time. Then they add in free gifts. They are famous for saying "but wait, there's more." What they don't tell you is that you will have to pay a high shipping charge for each extra item, which might be worth more than the freebie.
Check out your dollar store. Sure, the commercials say that the product isn't sold in stores. However, there are some "as seen on tv" stores in the mall. This way you can get a feel for the product even if you decide to order it off the TV. You can often find similar items at the dollar store for a lot less money.
Say goodbye to the money back guarantee. Many infomercial scams offer money back guarantees when they won't even be in business in a few months. These guarantees can be a hassle to get. Don't count on the money back guarantee even though some infomercials are legitimate. Ask yourself if the deal is worth it even if you don't get the guarantee.