Ask them about their job. This usually ends up with you being attentive and interested in their respective profession. It's such a great conversation opener because it already shows the personal side of the one you're talking to.
I feel like this is the general go to conversation starter but I'm not a fan of it, I feel like people are too defined by their work and I don't like that. I try to ask people about their passions and their dreams, it's maybe a bit more personal but it's such a better conversation and for some people they may end up talking about their work anyway. Or you could talk about the weather