This is a great question and I wish I could distill the main take-aways into tangible things that could be used to effectively guide people away from fascism. Here's my experience:

• Went to a decent university. Met people all over the political spectrum. Made friends with other far-right people and found them to be bitter, weird and kind of dense over time.
• Studied abroad for a semester, getting first-hand experience on what life in a foreign country could be like. Got help from a lot of decent folks.
• Met people from groups I used to hate. Realized they were just ordinary people and not sinister demons out to get me.
• Moved away from my far-right family.
• Got fucked over by other far-right people, who used shady tactics and unfair practices they were accusing other groups of.
• I used to love debating, so I had lots of discussions over a few beers with incredibly patient and validating people from other parts of the political spectrum. These arguments made the first cracks in my belief system.
• My country shifted from a left-wing government (in name, at least) to a right-wing one. I thought the left-wing government was corrupt and incompetent. The right-wing government quickly turned out to be that and more. When they started to agitate people against people fleeing from war-torn Syria to win the next election, I did a full 180, volunteering to help and going to protests, remembering the time when I was trying to get by in another country (as a privileged brat, not an asylum seeker).

I think that's it, but there are probably many more minor bits that contributed. Ask me anything.