Indoor flying can be hazardous, to say the least. Obstacles, debris, and prop-wash are all very dangerous. Here, more than anywhere, is where it's important to go very slowly.
Before you begin your flight, you'll want to check for items that could get blown about. If you can't run a leaf blower in the room you're flying in … you can't fly. Indoors, I've lifted and flung area rugs across the room, seen ancient dust bunnies come out of the woodwork, and had papers shredded in my blades. I learned the hard way to do this check before I fly indoors.
You'll also want to consider possible air currents. Stay away from the walls. You'd think that walls would create a buffer of high pressure and push you away. The opposite is true. The closer you get to a wall, the more it tries to suck you in towards it. The same goes for ceilings too. Any obstacle can create a wind current. Analyze the room, and try to predict any wind currents that could disrupt your flight.
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