Yeah - where are these damn aliens??
Lets hurl lights into their eyes to see if they can see, and ram needles into their nerves to hear, if they can feel..*
Or maybe just have a chat.
They could turn out very similar to us, actually - along the lines of convergent evolution - it's not unreasonable to imagine, they use the camera-principle for their eyes for example..

*Stole this and modified it - is a quote and forgot from where - but "hearing" if they feel comes from recording nerve-signals and transforming them to audio, like it is done sometimes.