If you do not have privacy issues, it is best to leave bay windows uncovered by shades or blinds. This will showcase the view outside and let light into the room. If you do have privacy issues, the most attractive shades to install are Roman shades, which are straight blinds that gather at the ends when pulled up. Avoid using blinds. Blinds, with their horizontal stripes, clash with the clean vertical lines of a bay window. Straight, simple curtain panels also look great on bay windows. Consider hanging a panel between each window. Hang the rods high on the ceiling for a dramatic effect. Avoid swooping valances, which can make a bay window look too formal and ornate.
Furniture and accessories are also important. Often, homeowners set a large sofa in front of a bay window and call it good. This is not a proper use of space, and it completely cancels out the interesting architectural detail of a bay window. Instead, consider creating a sitting area. Place a lounge chair at an angle on one side of the window, and a small table next to it, along with a floor lamp. Add a plant or two, as the natural light from the window will benefit any nearby plants. If your bay window is in a kitchen, place a small round table next to it, creating a breakfast nook.
Finally, consider building a window seat. A simple seat can be made out of plywood. Have a friend measure, cut and assemble the pieces, or do it yourself if you are handy. You can even take the measurements to your local hardware store and ask someone to cut the pieces for you. Once assembled, place a cushion on the top, and warm it up with some throw pillows. If you are especially handy, you can even build or sew some pockets into the front of the seat to hold books. Add a wall-mounted lamp, and you will have yourself a cozy, miniature library.