I think God wants to hear from us, so we should let him know what is on our minds. I can be very specific about what I want at times, of course I always know that if it isn't what God wants, I won't get it, but it seems to me that is always implied in a humble prayer anyway.
I often times try to relate my own fatherhood, to God's fatherhood as I believe he gave it to us as a gift, which helps us know him better, and his desires for us as his children. For whatever it is worth to you, I can say with certainty that I don't want my own children simply telling me "whatever you want, dad", but rather I want to get to know them, and what is on their mind. I want interaction with my children, and I think God wants that with us as well. If they want something specific, then I want to hear about it. I may ignore the request, or I may grant it, but either way I'll have an intimate 'parenting moment' with them.
Your own mileage may vary