Internet marketers live on global networks, hiding in dark niches and hoping to fall into the trap of innocent users who fall victim to their talents. They offer guarantees that they know you're too lazy, promises that even an authorized agent can't make, and prices that are always above what a reasonable person would pay.
It is very easy to lose a lot of money to these people and it is often difficult to get it back even after the "guarantee" process. So how do you know if the product you're looking for is a good one?
The only real answer is word of mouth. Before you buy, do some product research and see what other people have to say. Reviews, comments, opinions, complaints ... you have to see them all. It might be annoying, but it's worth it.

Brand Insights

Dangerous Use of Abbreviations - Too many "review" sites are trading partners who expect you to buy from their website and immediately get a great user experience. You can tell these people that they have almost no problems with their product - and only rate one product (or group of closely related products) at a time.

Purchase information
Customer experience statistics
It's best to find a website that categorizes broad product groups, isn't afraid to distinguish the good from the bad, and deviates from bold graphics, bold titles, and other brands.

There are a few tricks you can use to keep it working if you can't find an honest review site. If you're considering buying a digital product and want to know if it's good or not, here's the list:

DO: Google for the product name in quotes and the following: "inurl:forum". This will take you to a forum (message board) where you can (usually) get honest feedback about the product of your choice.

DO: Google for the product name in plus quotes: "+ waste". Of all the words people often use to describe bad deals, "junk" is one word that traders rarely use. Criticism is another good thing.

YES: Check out the money back guarantee for most of these products. The default is 60 days - but that's not the important part. The important part is: will the product have a real effect during those 60 days? If you are not guaranteed employment within 2 months, this guarantee does not apply.
NO: Google for the product name and any of the following terms: cheat, suck, work, work, review, reason, comment, or the plural or gerund of those words. These are all words used by marketers who purposely create their titles to tempt you.
NO: Buy *anything* that has more than two similar "reviews" on the first two pages of Google. This is a product sold through marketing, not real efficiency.