what about the room itself? what colors will you be putting on the wall? is there also wood trim? what style appeals to you, formal, casual, romantic, modern, cottage????
there are some great sites on line now which show rooms fully decorated. Why not look at some of those (houzz, hgtv, pinterest) and see what rooms appeal to you. You may find something you'd like to emulate. others here will have more links for you and good suggestions.

First thing to do is post a photo of the room.

It is so hard when you need to do everything to a room! A couple of suggestions: Begin by looking at every available source to amass an inspiration book. You might identify a common theme among them, such as "red rug". Shop for the big items (sofa, rug). If you find one of those you love, you can buy it. Of course, then you are looking more specifically for the second large item to coordinate with the first! If you really like rugs, it can be a good idea to get it first, and then choose fabrics that coordinate with it. In my case, a rug said "take me home", and so I needed to change sofa and chair fabrics to work with it.

I would wait to do the chairs after you decide on a rug and sofa. It will be easier to find upholstery fabric to coordinate with the new sofa and rug, rather than the other way around. After years of working around my rug (which is very ornate), I finally gave up and went with a solid neutral sofa. And I'm going to use the pillows to bring in the color I need.

I would decide on a rug first, then sofa then chairs.

You need a jumping off point....is there a favorite piece of art you will be hanging in there..if so...then pull the colors from there. A rug is also a good place to start. Go through magazines or websites like houzz and find a look you like and go from there.

Let's see:

1) Really sit around the whole room -- in every chair and seat. Look. Look. and Look Again. How do you want the room to feel? Warmer? Cooler? More Open? More Cozy?

b) Really write down any issues with the room at this point ... seating for how many? tables? shelving for storage? Is the room too dark (or have dark corners?) too light?

c)HOW do you want the room to work for your current needs? TV? Reading? Conversation?

2)Measure Everything. And write it down. Really. Measure the room, walls, windows and doors. AND hallways -- too many folk have bought a wonderful sofa/armoire/shelves -- only to find that their perfect item won't fit through the front door or down the hallway! :)

3)Start collecting inspiration photos from all kinds of sources. Really examine photos -- and decide WHAT and WHY something takes your eye .... color? shape? texture? arrangement?

4)Find a starting point. Usually start with a larger item -- like a sofa. Then decide on your needs for additional seating options -- chairs? loveseat?

5)Keep an eye on your local stores -- and search your local Craigs List.

6)Find the next item -- usually a rug or additional seating. Choose one -- and then -- look for the other one.

7)Once the main items are in place -- look again. What tables are needed?

8)Lamps. Lamps. Lamps. Table ones. Standing lamps. Always have lighting options! :)

Thanks for your thoughtful and helpful replies! I'm going out of town for a while but will try & get photos up when I return.