How many people buy into the much loved "if you don't do this and that you WILL DIE!" shpeel? Funny how you never knew you needed whatever it is until someone tells you.
We are a gullible lot. We don't seem to know it though and the only people who do know it use that knowledge to their advantage. This is not limited to actual adverts, there are so many things that you can do to make someone believe you. Just think of every person who was ever a leader - they were all adept at selling themselves and whatever their message was.
Even doctors are all about selling their services while the willing patients go along, unquestioning. In this particular case we simply assume that a doctor would know what they're talking about and so will do every little thing they suggest - but if you were to look at statistics of how many people die or are compromised in some way because of a doctor's mistake then you may realise that our assumption is flawed.
It doesn't take much to be a good salesperson. You need to be able to convince your customer that what you are selling is what they NEED, even if they didn't even know it. You need to be likeable - people do not like buying things from people they don't like. It helps if you're attractive and/or have a "nice" voice (Yes, this has actually been validated in studies). You should be well dressed. You should be charismatic - make people feel that you truly enjoy their company and that you value them. Be skilled at reading body language and verbal cues, and then how to exploit this. You should be able to make your customer believe that they are making a good choice by buying what you're selling, even if it's only during the moment that you're making the sale.
Now for all of the suckers, first you need to realise that: even though you may believe that you know best, or that you know exactly what's going on in every moment (especially when it comes to the motives of other people), basically that you're not as smart as you think you are - then you can come back down to reality and start looking at situations objectively. What salespeople do is play on your emotions to influence you to want something, to lead you to believe that you need this thing and that it will improve your life in some way. One you are open to this reality you, in a way, free yourself from getting caught up in the sales pitch. It is safe to assume that, in most cases, every person you meet (especially when they are selling you something) has their own interests ranked as Number 1 in their lives and minds, so everything that they do will be for their own benefit. It is not a very nice truth, but that doesn't make it any less true.
Once you are not getting lost in the dazzling smile of every pretty picture or salesperson you can start seeing how all these things you're being propositioned for are not always what they initially appear to be. It also gives you the space to recognise that some things require more investigation before committing to them. All in all, you give yourself the opportunity to make informed decisions.