Lighting is an important consideration. No artwork of any kind should ever be hung where direct sunlight will fall on it. The high energy of sunlight will fade the art and weaken its paper or other supports. Fluorescent light also contains a large amount of the most damaging frequencies of light. Fortunately, there are new glazing products which filter 99% of the most harmful part of the spectrum, helping to protect against such exposure.
Glare or reflection from glass may be of concern. Ultimately, reflection from the surface of artwork may best be controlled by placement of the art relative to the light source and the viewer. Ceiling-mounted spotlights are very effective, because their reflections bounce down to floor level. Similarly, table or floor mounted up-lights can provide a dramatic effect while reducing glare. Sometimes it is difficult to avoid reflections of lamps, windows, or other light sources that are near the viewing level of the art. These can be controlled by "non-glare" or optically coated glass which is designed to break up reflectivity. Today's non-glare glass is much clearer than that available in years past. Anti-reflection glass is designed to be virtually invisible in most situations, even when used with multiple mats or deep frames.
In addition to controlling light exposure, it is also important to avoid hanging art where it would be exposed to extremes of heat/cold or humidity.