Never share your present wage. It's none of their business.

They may not do it, but it gives them every opportunity to reduce your salary from what you might have gotten.

Best response is to know your value on the market, how much you value your time, and try to find out how much they're getting paid. Then you negotiate your rate with them having as much knowledge as possible. You can ask what they pay their current people, but you'll have to take it with a little more salt than usual.