Posture:

Maintain a neutral body posture, including back, neck, shoulders and wrist.
Decrease forward reaches, get closer to your work.
Elevate your foot for support while standing and also as a weight shift for your lower back.

Stretching & Exercise:

Initiate stretches and posture changes every hour throughout the day.
Pacing yourself and the speed of your work, especially when time or volume allows, helps to decrease fatigue.

Wear good, supportive shoes for prolonged standing or walking.
Use shelves at waist level for the heaviest boxes/lift and place the lightest items on the higher shelves.
Use of headsets for prolonged use. Alternate side of the neck you prop the phone on if you do not use a headset.
Alternate activities / work tasks and postures. When possible alternate those that will also allow you to alternate muscle groups being used.
Writing, proofing or reading with your work on an incline (i.e.: using the angle of a notebook) so improved posture.
Using the rubber thumb tips, tacky gum or wide / rubber tip end pencil to sort through papers.
Avoid resting your wrists or elbows on the edge of the work surface.
Avoid tight clothing, bracelets or watches that might impair circulation in the wrists.
Cold packs / ice can be used to decrease immediate symptoms / discomfort including swelling.
Using appropriate size fitting handles and tools to maximize strength and comfort.