This really should be a subheading of the "how to be a customer" guide that all diners need to read but we can just start with this piece.
Here in Northern California we seem to have the greatest concentration of self-styled vegetarians in the US. Not too many of them meet my (and most chef's) definition of a vegetarian which is simple. You don't eat dead animals, period. In my book, vegetarians don't eat fish or poultry. They don't order tofu with gravy that contains chicken stock. They do eat milk and cheese. I'm pretty iffy on the egg thing. I mean, you don't want to eat the dead animal but you'll eat the egg ? That somehow seems more barbaric, if your motive for vegetarianism has to do with treatment of animals.
Most vegans seem to be clear about their definitions, although I have served calamari to a "vegan", albeit without aioli because he didn't want to eat the eggs, and know a "vegan except for bacon" woman who claims her body needs the bacon.
To get down to it. If you're one of these "vegetarians" who really eat everything under the sun, but prefer a mostly vegetarian diet, don't proclaim yourself to the waiter as a vegetarian. Just look at the menu, find what looks like fits your particular fantasy of vegetarianism and order it. If you're unsure, ask your waiter, but again don't claim to be vegetarian. Doing so just makes real vegetarians look like nuts to food professionals.
Don't get me wrong. I'm not advocating any particular diet or combination of foods as being better than another. I'm advocating an end to hypocrisy. Eat what moves you, enjoy it, be who you are. Just don't tell me you're a vegetarian and tuck into a nice roasted chicken.