Brakes

I went to the tire store the other day to get new tires and as the mechanic was changing my tires he called me over and told me that I would need new brake discs because the discs are low. I was just wondering if I should believe this because a lot of the times these people like to tell you stuff that isn't needed until a couple months later, so you will buy brakes from their store. I was just wondering what type of brakes I should get? And if I should just bring it to the dealership instead to see if the brake discs are really needed?