You should experience no pain when your orthodontist applies braces to your teeth. Of course, every person's tolerance for pain and discomfort is different. But during the procedure lasting 90 to 120 minutes, you should know it's not supposed to hurt. Definitely alert your orthodontist of any discomfort.
Immediately after getting braces, you should be able to go about your day. What and how you eat is the only thing you'll need to do differently. It's best to stick with softer foods you don't need to chew – or require minimal chewing – for the first few days.
Before getting braces, it'd be a good idea to stock up on a couple or three days' worth of soup, yogurt, mashed potatoes, mac and cheese, yogurt, applesauce, pudding, and ice cream. (That sounds pretty good, doesn't it?) If you slip in some chewy food, it might take you longer to eat meals as you adjust to chewing with braces.