Freedom in filmmaking means that you have the ability to film exactly the type of scenes that will tell your story best. You should not be forced to change or alter your vision strictly on the fear that you may not be able to perform under certain limitations that may be in front of you. One of the most difficult to work with is an extremely small room, which limits the movement of the actors and the placement of the equipment. Here are a number of tips to help you work around these constraints.
The first thing you have to think about is exactly how small the room is. Are you going to be able to fit all of the equipment in there? And if you cannot, then what are you going to leave out? Figure out exactly how much room you think the actors are going to need to perform the scene. Try to cut your original movement vision in half, making consolations just as the characters would in this given scene. Most people have a certain pattern for their physical movement and when they get into tight locations they spontaneously modify their movements. You will also have these kinds of problems since you will have a general idea of how those movements will occur. Be assured that you will be able to modify these for the small space.
Think about what light you are actually going to need. The best choice is to use only a single light and see if you can use it hand held. Try a large scoop light and then diffuse it with a screen so it acts as a fill. This will blanket the small space with diffused light. Try to lift the light as high as possible to give it the most spread over the room. If you want to mimic a solitary light you can just take the screen off and you will end up with a much more dramatic falloff, possibly even a hamlet-esque silhouette.
The camera is going to be hard to work with in this set up so try going without any type of stand, unless it is a monopod. Then try to position yourself against a wall or door frame for stability and to limit shakiness. Look at the position of the door and see if you will be able to get main action without even stepping into the room. If you can shoot through the door you will end up with much more freedom and stability and the room will have a better visual.
Run through the scene several times and see how things work out. Use wireless lavaliere microphones when possible because putting in some type of shotgun will just be in the way. If you cannot place them on people just place the lavaliere's at different hidden spots around the room.
Play It Out
See how the scene works and try to use the limitations to your advantage. Let the room end up playing a character in whatever scene you are crafting.