Talk to them. It doesn't matter whether they can understand you or even recognize a "you". Talking is mostly a thing we do with humans; it's an empathetic impulse. And if you're irrationally afraid of the creature, talking aloud can calm you down. It can reframe the interaction from one of a person versus a threat to two people who are both making the best of their situation.
Call them "them", or gendered pronouns if you must; do not call them "it".
Get up close and get a good look at them. Seeing someone from a distance engenders psychological distance; seeing them in poor detail engenders poor understanding.
Get curious. Imagine what it's like to be them: that's basically the definition of empathy, but you don't have to do it for empathetic reasons. You share the planet with a multitude of very strange creatures who are very different from you and live odd, alien lives. Habitual curiosity about their subjective experiences can become habitual empathy.
