Or, “What would be most helpful?”
If someone’s ever nice enough to ask you this, it’s generally a good idea to have a pointed, specific, answer to this question. It just takes a little bit of preparation before the meeting, or even a more intentional mindset during the meeting, to see how the other person can make a contribution.
If you’re trying to help someone else, and they don’t have an answer, you can even go a step further. “Would it be helpful if I…?”