Brian Nguyen: Camera operator, director of photography and first assistant camera in Los Angeles, California.

Both Brian and John offer some great advice Hayward. I would also suggest bringing along your Gaffer, if available, so there will be clear communication on the day. As mentioned before, try to go around the time of day you plan to shoot, but also take into account what the weather may be like on the shoot day. You may have clear sunny skies during the scout, but on the shoot you could have something dark and gloomy. Someone from Art Dept. should also be there, this way if you see something that may make your shots less visually appealing, you can get with Art Dept. and come up with a plan for the day.

Good thread. I'm learning cinematography soon.

Good advice given above. The main thing I'm looking for in an interior are windows. If there are windows, know what direction they are facing. It's not always practical to scout at the time one will be shooting (although that is ideal). Often the scout happens before the schedule is set. Use a compass and experience or a sun tracking app to determine if sunlight will come through any windows and at what time of day. Is the location on the first floor? Can sunlight be blocked from the outside if necessary? What will the equipment load in be like? Are there stairs, an elevator? Where will equipment be staged out of the shot? The next thing I look for is practical lighting. Is it tungsten, mercury vapor, fluorescent? If you have flos and don't have a color temp meter, look at the name on the tube and then look up the nominal color temp. You can expect a certain amount of green in most flos. What is the existing light level based on desired camera ISO? Use a light meter or take a DSLR camera along. Also, take along a tape measure for measuring things like windows (for gelling) and doorway widths for dolly shots. How high is the ceiling? Is there anything like beams, etc. that lights can be hung on? Is the floor smooth enough to dolly on? Of course the first important considerations are aesthetic - like architecture, size of space, furniture, wall colors, and general appropriateness to the scene.