Mostly, we talked about our plans for the day. When we went in September, the lines were fairly reasonable. I don't really remember waiting in line for anything for too long. In Soarin', they have a game on the wall that you can play on your phone. I took that everywhere with me, and I played even if I wasn't technically in the Soarin' line.
I also played a lot of Pokemon Go. And I took pictures of everything. When we were in the Soarin' line, we were making our guesses aloud to each other, and the family behind us asked what we were doing and how to play. So we ended up talking to them. (That was really fun!)
We also ate lunch at a table in Be Our Guest with a pair of women we didn't know, but they were super nice, so it wasn't too uncomfortable. I think my strategy when talking to people at Disney isn't so much 'Oh hey, I'm striking up this conversation purposefully' and more 'This just kind of happened, but I'm okay with it'. And at the end of your vacation, if you're getting tired of your present company, it's totally welcomed to talk to people outside of you and your family. I had had enough of my mom by the end of our trip in September. I love her, but it was nice to talk to other people!
You can always get a Hidden Mickey book and try to find them in the queue. There's always the strategic planning of your next ride from wherever you are. I tend to zigzag all over the parks, but other people might make a beeline for a ride that's got a much smaller line. You can always check/double check your ADRs or pre-plan your meals. I had done all of the planning, so I caught my mom up on what we were doing and she looked at the menus on her phone so when we got to dinner, we had a plan of attack.
I can't wait to try Heads Up in April! That'll be fun!