Growing up, my whole family ate meat and I always took the view that it was necessary, afterall, other animals ate meat too, why shouldn't we, so I never used to have any quals about eating meat although I remember being very opposed to the fur trade and foxhunting even while I was an ardent beef/veal eater as I thought it was totally unnecessary and cruel.
When I was 15, I made friends with a kid called Patrick and his friend King, who I'd go skateboarding with in the summer when I visited my grandparents in Russellville, KY where they also lived. They were both Vegan (though I know King went back to eating meat a few years later). At the time I thought the idea of Veganism was stupid and posed rediculous hypotheticals to them (you know the ones: 'What would you do if you were on a dessert island and there was nothing to eat but a pig lived on the island?' etc) but a few years later when I was 19 and had just finished high school I gave up red meat on a whim. I have no idea what really prompted me at the time but I think it was for health reasons but anyways, shortly after that I made friends with a bunch of Vegan kids in Nashville who urged me to read 'Diet for a New America' which compelled me to give up all meat and fish but not dairy products or eggs (although speaking to Patrick on the phone around that time also helped me to really understand why he'd gone Vegan at 15 and still was 4 years later) because at the time I was living with family in KY and didn't want to be aukward. I had decided I would eventually go Vegan which I did eventually last February when I began to think about my diet and realised I hardly consumped any dairy products and at that point had been thinking about products that were tested on animals as well etc.
Also, I wrote a documentary script on Veganism in college this year (I'm not especially proud of it but that's another story...) but researching it was really eye opening as I learnt a lot about the egg and dairy industries I was totally unaware of previously (i.e. the slaughter of male chicks/calves as 'waste products' of the industry) which has made me even more passionate about my beliefs (but not in a dogmatic sense since I don't think being dogmatic and self-rightious helps our cause at all, the key is to be understanding and sympathetic in my opinion anyways- I'm fairly sure if I hadn't made friends with such understanding/friendly Vegans I would not have even considered it).