Leigh Ann and I have found that planning an inquiry with students is a must, it's a lot of fun too! We are still learning how to make student's voices the loudest but we've found this idea a great step in the direction we are aiming for.
We use Kath Murdoch's Inquiry Cycle (found HERE) on the IWB, or you could do this with marker on large poster paper, to plan a basic overview of our inquiry ahead. It's a great visual and way to manage time with a longer inquiry unit. We return to it during our inquiry to check our time progress and make adjustments to our plan as needed.