I'm sure plenty of GMs already do it, but for those of us newer to this side of the game screen it could be helpful, I hope. I guess it varies depending on each group, but I've found that my players very much prefer when I treat what they say at the table as what's being said in the game, within reason. Even when it's against their best interests, like when a shopkeeper angrily tells them to get out after hearing them openly planning a robbery, is usually funny enough to be worth their trouble and works to make your NPCs/environment more alive and real. In addition to "real time role play", you can also grab quirks/mannerisms off of them and turn it into a story element. An example I have:
One of my players quotes from the Gladiator movie every single session we play in, in particular he shouts, " Open the gates Proximo! Do you want to die old man!?"
After four sessions it still makes me laugh, so I've begun rolling a d100 once a session when he says it. If it ever hits 100 an old friend of his dead family named Proximo will be on the other side of the gate, thrilled to see the little noble all grown up and alive. And just like that I have something that makes my players' story a little more special.
Just a small suggestion to GMs looking to add something extra to their RP or story. I'd love to here other tips or thoughts on the matter from the experienced ones here.