Where will the label be used?
In what environment will the label be used?

Will labels be used indoors or outdoors?	Label materials come in indoor grade and outdoor grade. Outdoor grade materials are more resistant to sunlight, rain and variations in temperature.
Will labels be exposed to water?	Although a label may be used indoors, it still may be exposed to conditions that will cause the label to deteriorate. For example, paper labels should not be used in locations where they might get wet. Also, some inks used for printing are water soluble and will smear when they get wet.
Will labels be exposed to high or low temperatures?	Low temperatures can cause some label adhesives to become brittle and fail. Labels are available for cold weather, cold storage and even for labeling items stored in liquid nitrogen. High temperatures can cause some labels to become discolored or blacked out. Label adhesives can soften and fail.
Will labels be exposed to chemicals or solvents?	If labels are exposed to chemicals and solvents, then chemical resistant tapes and inks must be used to create the labels.
Will labels be exposed to oil or grease?	Oil and grease can damage some label materials and inks.
Will labels be used in low light, or no-light conditions?	If labels are needed in low light, or poor visibility conditions, special highly reflective materials can be used to increase readability of the label. Glow-in-the-dark labels can be used in situations in which it is necessary to read the labels when there is no light.
What type of surfaces do labels need to adhere to?	The type of surface the label is applied to affects the type of adhesive that is required. Adhesives are available for smooth, rough, fabric, dusty and other types of surfaces.

More: What do I need to know
before buying a label printer?