Very important information from Dr. Greger from nutritionfacts.org on vitamin B12 supplementation for those who eat only plant-based foods, i.e., vegans. Source: NutritionFacts.org Updated Vitamin B12 Recommendations Infographic
One of the hardest things when moving from a meat-based diet to a plant-based diet is actually how to get started with it. When I did it myself 7 years ago, I realized it's essentially a matter of educating yourself. Most of us grow up in families and cultures where animal protein is at the center of our plates. When we first learn to cook we are essentially taught to decide on what animal protein we'll put at the center of the plate and then decide what to surround it with. It's a great relearning to make a transition from that. Below is a link to a guide from the masters of the whole-food plant-based universe, the good people at Forks Over Knives. I hope it helps you to get started. Beginner's Guide to a Plant-Based Diet