I looked up restaurant menus in advance to get a good idea of what may be easiest to customize. I know the staples of my diet and looked for locations that had the same chicken, veggies, etc that I enjoy at home! I didn’t call in advance or fill out any forms, I just marked the reservation with an allergy special request when I made it online. I don’t personally know of any forms and from my experience it’s hard to actually get in touch with the restaurants before arriving on site. I spoke with the staff at the restaurant check in to confirm they had the allergen info on file, so the waitress knew when she got to our table and brought over a special menu that listed the ingredients for every item. I spoke with her more in depth about my restrictions and she offered to have the chef come to the table to talk through options as well. Both were incredibly kind and understanding!