Get enough calories, especially if one decides go go vegan. Ounce for ounce, vegetarian and vegan fare has fewer calories. This good if one is trying to lose weight, otherwise not. Iceburg salads don’t count as a substantial vegetarian meal.
Fake meat and fake milk are optional. The quality–in terms of taste–of fake foods is hit or miss. I suspect many people are discourage from becoming vegetarian because they figure they’ll have to eat fake meat to make up for the absence of real meat. Tofu is highly overrated in this regard. I find it easier to cook with seitan instead. The best ‘fake’ foods are homemade recipes which don’t try very hard to replicate the real thing, but do try to be good to eat.
Getting enough protein can be done by accident, but getting lots of vegetarian protein takes planning, say for pregnant women or weightlifters. Ounce for ounce, vegetarian and vegan fare really does have less protein. Somewhere in this blog I have a post about strategies for eating lots of vegetarian protein, but I’m too lazy to look & link it.
Beware of dietary perfectionism and isolationism. Having a strategy for staying socially engaged with the non-vegetarian world is probably as important as learning the new recipes. Flexitarianism, a word I’ve just invented maybe, is eating vegan when it is convenient to do so, vegetarian when being vegan is to difficult, and eating low on the hierarchy of sentient beings when it isn’t possible to be a vegetarian. Being flexible may sound unprincipled, but making no effort what so ever to consider the impact of diet one’s health and the surrounding world is doubly unprincipled.
[this started out as a comment on another blog that got too long]