As far as your vision is concerned you have it, now try to break it down at higher level than you have without thinking much about implementation. You'd need to think about implementation, but not right away. Abstract can go long way at least right now.
Put yourself in your users shoes and think how will they interact with it i.e. i'm standing outside the meeting room with thing ginormous tablet staring at me, now what? Let me touch, push button, aah, it says room is available and there is a button that says "Start reservation"....
This is called a metaphor or use-case, then you worry about your calendar, database, resource, connectivity, good looking UI etc.
If you already have that figured out, its time to do a proof-of-concept. Implement room booking for Friday 13th, March 2012 at 9am to 11am for group of 3. Then start generalizing and keep adding beef until you're satisfied with tenderness/firmness as the case maybe to your liking :-)