I believe that the first way to avoid getting scammed is not being greedy and believing in something for nothing, secondly not seeking the easy way to achieving a great financial success.
You nailed it with those two statements. If you check very well, the majority of the people who fall into the victim or scam were because of their greed and the belief that there is free money out there. Once you are greedy and want free things, then you become the number one target for scammers. They will sell that idea and information that you so much hope and desire for to you, and you will end up buying and believing it without even giving it a second thought because that's exactly what the person was expecting.
Always, that saturated looking too good opportunity with the potential that it'd bring quick rich is what lures most people victim of scam and so it's executed on the greeds who strives to use a less amount to get rich in a quick time.
Their ignorants and greeds neutralizes their ability to verify before accepting that too looking good offers.
Sometimes they considers the capital to be too small to attract scammers without thinking that when a lot of them has been victimized, the scammers is at the end realizing a huge sum of money because those vulnerables think scammers will only be interested on big amount of money.
On the serious note, most of those vulnerables have to convince themselves out of their greeds of getting rich with less risks in a short time even before they gets on the scammers targets so, it becomes easy for the scammers to succeed them.