That's what I've found, just ask. Sometimes your most outlandish request will be met with, 'how would you like that?, or 'do you want me to do it while also doing this?' A good way to ask is, "Have you ever had a customer ask you for X?" Then, they know you are interested in doing X, but you haven't directly asked them. If they have done X, they will let you know they are also willing to do X with you. This has worked for me every time. Sometimes you get answers like, So and so has a customer that she does that for and we have talked about it, it sounds fun. What she is saying is, yes I have done it and will be happy to do it for you.