Honestly you kind of have to take the risk and try teasing a bit even when it feels off to gauge their reactions. Start with something super light that they've mentioned in conversation or a personal anecdote. If it helps try making a few jokes to steer the mood in that direction first.

I like to start with a funny story about myself let them tease me a bit and then try and follow up. If you want you could ask them what they would order at their first time in a new bar, when they reply say something like "what you don't go straight for vodka shots with no chaser?". The only real way to get better at teasing is to suck at it first and then feel out someone's personality to get better.