Restaurants on Rome's tourist piazzas (Navona, Trevi, Spanish Steps) are mostly overpriced tourist traps with mediocre food.
Walk 5–10 minutes off the main squares. Trastevere, Monti, Testaccio, and Pigneto have far better trattorias.
If a restaurant has photo menus, multilingual menus, and a host outside trying to lure you in, walk past.