You are in luck if you get to make the reservation in a business or social situation.
Use the Open Table app and website. It tells you what restaurants are in the area and they are rated by other diners. You can also look at the menus online. If there are some dishes that you know you can eat with a little modifying, call the restaurant and talk to the manager or chef. Another great tool is the Happy Cow website and app. You can look up plant-based restaurants in any city.
If you are at the mercy of someone else making the dinner plans, explain your dietary needs and ask if you can find out the restaurant ahead of time so that you can contact them.
Find a few neighborhood restaurants that will work with you. You will be surprised how willing the chefs will be to accommodate you if you explain that you live in the area, will go there often and have a special diet for your health.
It is important to stress to the restaurant that this is for a health reason; you are not allowed to have oil. Otherwise, they make try to sneak it in. Explain that you need a vegan meal (this may be a more familiar term) so no animal products and no oil.
Here is a list of different types of restaurants and what you may be able to modify:
Steakhouse - at the very least you can usually get a plain baked potato, steamed vegetables and a salad with lemon or vinegar. Make sure to verify that the baked potato has not been rubbed with oil (yes, this is common).
Indian - often-times good for a plant-based meal. Dal usually has the least amount of oil of all the dishes. Ask if they can prepare the dal without oil.
Italian - can be okay if their pasta is made without eggs You can get them to sauté some veggies in white wine and throw it over the pasta.
Mexican - can be good, but it can also be full of lard. Ask if the black beans, tortillas and rice are vegan and without oil. You can put salsa or Pico de Gallo on your rice and beans and have a great meal. Be sure to bring your baked organic tortilla chips from home to dip in the salsa.
Pizza - you have to call around to find a pizzeria that does not make their dough with eggs or oil. It may take a few calls, but you will find some places. Order your pizza with a tiny bit of sauce, no cheese and any raw veggies that they can cook on the pizza. In other words, stay away from things like grilled onions etc. That means they have been grilled in oil.
Sushi - this is a fantastic option. You can get a veggie sushi roll. Often-times there will be avocado in the veggie roll. If you are trying to reverse heart disease ask them to make it without the avocado.
Japanese, Chinese, Thai or really any Asian restaurant - get steamed veggies and rice. You can sprinkle a little soy sauce on top.
Vegan/Vegetarian – you might be surprised that these are tough places to eat. The food is usually packed with oil, nuts and avocado. Call ahead and explain your dietary needs. They may be willing to work with you.
Mediterranean – beware, they use a ton of oil. There will be some chopped salads you can order without oil. Call ahead and see if they can make you something. They do use a lot of fresh vegetables.
There will be places where you simply can’t eat anything but a salad. You will have to go in prepared with your dressing or suffer through a meal of lettuce with lemon. That is really the worst-case scenario.
You can bring your own food in if you are eating with others in a place not of your choosing where your choices are limited. 99 times out of 100 if you are discreet the restaurant will not say anything.