How does someone SUE a fast food restaurant?

So I've read the stories of people finding things in their food at TacoBell the lady who sued McDonalds for burning herself etc... My question is how exactly does the ball get rolling to actually sue one of thes large corporations? Do you call them first and let them know; find an attorney who will take your case if it involves ingesting foreign matter that was in your food first? Send a sample to a lab first to see what it was and then call the company? I would appreciate anyone sharing whatever knowledge they have on the topic. The reason I ask is once I ate a IN N OUT BURGER and there was something really hard in the meat I almost dislocated my Jaw when my molar hit it, so I told an employee and the manager came out immediately and apologized a dozen times gave me some vouchers and quickly took the napkin with the object almost like they didnt want me to even think of keeping it. Its obvious why, I would have done the same. Well a few years later and I just had the same experience at Taco Bell, I can't tell what it is but it was in the ground beef, this time I kept my receipt and the particle in the wrapper, so what should I do, I was eating it for a few minutes until I bit down on it and it HURT like a mother#&$#@!. I would like to get it yzed before I decide how to proceed with this but I dont know how to go about that.???