Joe Henley's website, "Traveling on My Own Agenda" is a special find for travelers.  I am sure his straightforward and folksy style of writing will appeal to you.  I'm happy to have him tell you in his own words about his 3 favorite Florence restaurants here: 

I have been to Florence, Italy twice. The first was a day trip and the second was a four-night stay. I love to try new restaurants, but these 3 were so good, I will have to go back to them when I return.

Da Nerbone is on the bottom floor of Mercato Centrale. The address is Mercato Centrale, 50123 Firenze FI, Italy. It is one of the indoor food stands and it serves traditional Tuscan food. There are picnic tables nearby where you can sit, eat and watch the crowds. 
 
I have eaten tripe before and since it comes from a cow I have always referred to it as beef tripe. While I was in line and it was my turn to order, I quickly said Beef Tripe please. The guy making the sandwiches calmly put his knife down, put his hands on his hips, looked me in the eyes and said "Well, do you want beef, or do you want tripe." I promptly said, “tripe please”. I felt like I was on the Soup Nazi episode of Seinfeld. The sandwich was delicious, and the hustle and bustle of the indoor market was interesting to watch as we ate. I suggest trying out Da Nerbone and get there by 10:30 to beat the lines, order a sandwich and a carafe of wine and enjoy a meal and the ambiance of a different kind.
 
Trattoria Sostansa,  Via del Porcellana, 25/R, 50123 Firenze FI, Italy, is a restaurant you don’t want to miss. We had the best chicken breast I have ever had. The Butter Chicken Breast comes 2 breasts to an order and is cooked in butter. If you go with one other person, don't discuss what to order, just order it and decide what to go with it. We had the Tortini di Caciofi, a dish made out of artichokes and eggs and it was great! I have read that steaks are very good here also, but the Butter Chicken Breast is what to eat!  And make reservations. We arrived a little before the restaurant opened and there was one couple in line ahead of us. They were turned away because they didn't have reservations. 

Trattoria 13 Gobbi, Via del Porcellana, 9R, 50123 Firenze FI, Italy, is a fantastic place to eat Bistecca Florentina. The first 2 restaurants I had researched but this one we stumbled on by chance. We had tried to go to Trattoria Sostansa on a Sunday, but they were closed. We noticed some people waiting outside a restaurant a few doors down and decided to go there. This turned out great because I had one of the best steaks I have ever had! It is in my top 2 all-time best steaks. We shared a 2-pound Steak Florentine for 2, rare, a bottle of Chianti and delicious white beans. We got in without reservations, but I would make one because the place was full. 

Start Planning Your Trip to Florence and make these 3 restaurants part of your plan.

See more from Joe Henley at "Traveling On My Agenda"