For me it helps to be clear about my schedule in advance--especially if it is the same every day--"I'll be riding my bike every afternoon for 3 hours." This works because they value my fitness (and can't come with me).

I also rehearse forbidden topics and how I will not respond. I usually end up falling into the trap anyway, but sometimes I can just sit with a blank look and pretend I'm a wooden carving. This works better and better as we all age. I have also tried responding with an unrelated answer--as if I didn't know where the conversation was heading. A couple of times this has worked brilliantly.