look for places during the day that are crowded at lunch with locals and business types, then make a res to go there for dinner. they will often be the best/most affordable/least touristy.
also, i believe the old anthony bourdain show - "no reservations" - did a rome episode, he's suually spot on if you cna find a summary or see it on demand.
and finally - cacio e pepe or carbonara for pasta dish...never fettuccine alfredo (dead giveaway you're a nooob tourist)
Mike...NYC. My collection so far is a 312 and some cool straps.