I've lined up a couple of beta readers, and was wondering - do I just give them my first chapter, and ask for their opinion? Or is it better to ask specific questions about my work? (Such as, did you like the protagonist? when did you lose interest in reading it? would you read the next chapter?) If questions are the better way to go, what sort of things are good to ask?

I'm only going to be giving them the first chapter (about 5000 words) to begin with, because I don't want to overwhelm them. One's a writer herself, and the other's a big fan of the genre.