I usually go during off peak hours to limit the interaction with people with no gym etiquette. However the other day I was working on cable rows when a 50 year old lady walks up with a piece of paper in her hand and I immediately knew she was new to working out. Apparently her "trainer" had shown her how to use this machine, so she was clueless she was standing next to 4 other machines that do the EXACT SAME THING when she asked me how much longer I would be. I just said "One of us could use that machine there, since it does the exact same thing as this one, and since I'm already using this one, I think it should be you. Does that work for you?" She got the hint. I can't recall a time when I bothered anyone during their sets unless they were on the phone sitting on a machine I wanted.