Out of the light
Try not to hang pictures directly opposite large windows as sunlight fades colours and discolours paper. Special UV-coated glass can help to slow this down. The Fine Art Trade Guild has set industry-wide standards for printing and framing materials. Ask your framer about the ways in which you can preserve your artwork for the long-term.
Ideally pictures should not be hung above radiators. Extreme or rapid changes in temperature cause paper and wood to warp and dry out and adhesives to fail
Damp can cause pictures to ripple. If the ripples touch the glass, the picture might stick and be hard to remove. Damp also encourages fungal growth - likely to show as brown stains. Conservation framing can slow these effects, but it is always best to avoid hanging framed pictures in humid conditions. Allow six months before hanging pictures on newly plastered walls.
Remember most pictures are designed to be viewed at eye-level. When hanging a group of pictures of different sizes align the top edges. Groups of pictures need not be hung in symmetrical patterns, but they should follow some sort of overall design. Try arranging them on the floor first.
Using two hooks on the wall, set each about a quarter of the way in from either side of the picture. Check that the cord, wire or other hanger you use is designed to support the weight of your artwork. Where safety is critical, in children's bedrooms, for example, ask your framer about security fittings and glazing.
Handle with care
When carrying and transporting a picture, grasp the frame firmly on both sides. If you have to store pictures, make sure they are stacked vertically and the right way up. When stacking pictures, stand them 'glass to glass' so that the hangers do not damage the frames.