They're just like any other character. Full of as much life and utility as you give them. They can beep and honk, and most people seem to understand them.
Ex: "R2 beeped happily and followed his master into the diner." "The droid bounced back and forth. As if to say, Wait! I'm coming too!" "R2's head spun in circles like a comet. Did he really get asked out on a date!?"
You can infer the meaning through suggestion or, translate it directly. Like so:
Ex; ~ "Master Skywalker! The engines are burning!" ~
It's all the same. You're the writer so. Make it as colorful and energetic as you'd like.
And never. Ever. Underestimate a droid.
