At a high level, I have the same advice as any other instrumental rationality topic: know your purpose. Why do you want to move from small talk to more interesting topics? What anticipated future experiences are driving your choice to be talking with this person at all?
Specific options:
Accept social risk. Often, small talk is used among people who don't trust each other enough to open up. If you can identify that the actual risk is smaller than the perceived risk, then you can introduce the (somewhat) riskier topics that actually interest you. With luck, it'll interest them too.
If your goal is social cohesion, as opposed to your own entertainment or information-seeking, steer the small-talk toward the other person. Find topics they're interested in and guide them in telling stories about themselves.
Change conversational partners. If you can't identify a strategic goal in continuing a conversation, find an excuse to leave it and do something else. Do be somewhat patient, though: it's easy to underestimate the value of non-close acquaintances and the time it takes to get enough mutual knowledge to be able to have truly interesting conversations.
This thread is for asking the rationalist community for practical advice. It's inspired by the stupid questions series, but with an explicit focus on instrumental rationality.
Questions ranging from easy ("this is probably trivial for half the people on this site") to hard ("maybe someone here has a good answer, but probably not") are welcome. However, please stick to problems that you actually face or anticipate facing soon, not hypotheticals.
As with the stupid questions thread, don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better, and please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.
(See also the Boring Advice Repository)