How to become less gullible and naive?

I know that i am a very gullible person. I am usually the only person in the room who doesn't notice red flags. i always see other people making better choices than me. I feel all the time that i am in the dark because of this. Recently a guy was trying to scam me and my friend he is the one that told me dont trust him. I listened to my friend and my friend was right. What does my friend have that i dont have when it comes to wisdom.

How to become less gullible and naive?
How to become less gullible and naive?
Post Opinion