Windows are an important design feature of any room. Choosing the right window treatment based on your needs can be a challenge. Here I will list a few things to factor in.
Specific problems-All rooms have specific problem windows. Some are off center, odd shaped or serving no real purpose. Sometimes the best solution is to create an illusion of balance, purpose or shape. Sometimes a window that is off center can be balanced by creating the illusion of a second faux window opposite of it for balance, by adding another curtain rod and drapes that match. Of course this window would not be used and therefore the drapes would have to remain closed but it is a trick of the industry to create balance. Windows serving no purpose, meaning they don't present a pleasant view or really allow light in can have a small florescent light mounted at the very top and concealed with a valance to give off the illusion of sunlight.
Decide how formal of a look you are trying to achieve. Most dining rooms are usually a formally decorated area. Keep in mind the quality of the fabric of the window treatments you use in this area. If you pick a fabric of poor quality, it can very well cheapen the look of the entire space regardless of how nice all of the furnishings are. Save money by purchasing good quality fabric, finish off all rough edges with a simple stitch and purchase attachable curtain rings to allow you to hang them. Better to have Good quality fabric, and less detail, than cheap fabric that comes ready to hang.
Window treatment function-Windows that are designed to help circulate air flow and ventilation need to have treatments that will facilitate this purpose. Heavy fabrics will hinder the air flow, while too light a fabric will be constantly blowing and will do very little to enhance the window itself. Try to hang drapes so that they will be pulled back beyond the actual window at times when you are airing the house out. This way they will not blow into the room or hinder air circulation. Windows that allow for a lot of light, however will fade fabrics quickly. In this case you may want to opt for window blinds or lined draperies, again, make sure drapes can be pulled back beyond where the sides of the window are to keep them from fading.
Decor style-Depending on what style you are after, you may want to take into account what style the surrounding furniture is. You may have a mixed style and so you can easily pick one piece in the room that dominates the overall decor, or especially appeals to you and then search for window treatments and fabrics that were popular with that period of style. A little online research will help you in this process.
Decorative role- Sometimes the key problem is trying to decide what exactly will be the decorative role of the window treatments you do decide on. You will have to ask yourself, whether the main attraction of the wall the window is on, is the window itself, the window treatment, or any artwork in the room. If it is the window itself, choosing a window treatment that blends with the wall color will allow for the view to take center stage in the room. If the artwork you have on display on the walls is where you want the focus, choosing window treatments that correspond with a dominant color in the artwork will make you focus more on the artwork, while at the same time make the treatments on the windows compliment it. If the furniture is to be the focal point, you must choose window treatments that will compliment the color, or woodwork. The worst scenario is many focal points all competing with each other in the room and causing visual confusion and a lack of over all cohesiveness.