There really are roughly four major room types where you can use a projector. Of course there are all sorts of finer details as well:
This room will have virtually full control of ambient light. Typically that means if there are any windows or other openings in your room, that you have them covered, at least when you need the room fully dark. Sure, windows with blackout shades are fine, sconces on the walls or other lighting is fine, as long as you have the control of them.
And the last major ingredient is dark surfaces. Flat black, of course would be perfect, but few are than fanatical, preferring some atmosphere to the room. Surfaces should all, or mostly be rather dark or, at least close to it. No off-white walls, and it should have a medium to dark ceiling (and floors).
On the right, a projector set up in a dedicated home theater. The room has all dark surfaces and no ambient light pollution when properly darkened.
Never the best place for a projector, the traditional room has light surfaces. Ceilings and walls typically off white, or some other light color. Floors might be light as well – anything from blonde woods to light colored carpeting. Since most rooms do have windows, Orientation of the windows and some shades are important, at least if you plan to view it in the daytime.
You would be surprised how well some of the brighter projectors can handle such rooms when paired with the right screen.
Shown here, a temporary setup testing how a very bright projector (2800 lumens claimed) can do in a room that is a bright, light surfaced living room. A 1000 lumen maximum projector has no business in a room like this, unless only used at night.
Not as ideal as the dedicated home theater, but better than the typical standard Living Room / Family Room is the Multi-media room. You may not yet think of it as a multi-media room, but we're talking about a room that fits the bill of being better for projectors (or even LCDTVs) than the typical off-white living room or family room. If the walls are truly medium to dark, and the ceiling is off white, seriously consider darkening the ceiling 2-4 shades.
Since the ceiling is still going to be the brightest surface, it likely won’t seem darker when the lights are on, but it will help your projector’s image.
For the Multi-media room, windows need very good coverings. I’m thinking black out shades or close, but probably lacking channels, so light gets in around the sides.
On the right, a multi-media room. It has darker surfaces but a lighter ceiling--it's not quite a dedicated theater, but it's not a regular living room either.
While many people mount their projectors, fear not, plenty of folks (maybe including you) need flexibility. Maybe you want to use your projector in more than one room? Or more typically, perhaps you only have one room in mind, but on some occasions, it leaves the room? You might take it to your summer cabin, or more likely if you have a family, it might end up in the backyard for summer movie nights (or project onto your garage door).
For the small business person, it might help to have your projector double for business use, perhaps for an occasional presentation. If any of those things seem likely, then you will have multiple rooms to deal with. Some projectors are just more versatile, and thus better suited for you. Not so much the over $2000 projectors, but definitely for many from under $2000 to well under $1000.
Bright projectors, of course provide more versatility. Built-in decent sound that is great if you want to move it around, although there's no substitute for a good surround sound system. If you have business projector needs, there are projectors with some very good image quality for home while doubling for business. Consider your portable needs, but otherwise look to match your projector to the room that you will primarily use.
Here, a temporary setup (imagine for a Super Bowl party). The screen and projector are both portable, and not permanent fixtures in this downstairs common space with large windows and light surfaces. Not as bright a projector, nor is the screen ideal for this room.
Know that you've pinpointed the kind of room you're working with, we can move on to: screen size, viewing habits, long-term plans, etc.