I became vegetarian initially after watching the documentary Earthlings which really affected me. It was difficult for me because I grew up eating meat and I would have called myself a big meat eater. It probably took me 3-4 tries to eventually kick the meat habit and it was especially difficult when travelling to places such as Mexico which really do not have the options of say the US/UK.

Eventually I switched to vegetarian and then giving up the rest wasn't a big challenge for me as there are so many good cheese, milk and egg alternatives nowadays.