Sitting is preferred for fine work, exacting visual tasks, writing or light assembly work, and moderate manual work. Note the overlap between sitting and standing guidelines. Several tasks can be done sitting or standing, depending on preferences. Rotating between sitting and standing tasks is often beneficial. Unfortunately, they tend to be rather pricey.
Seated people are better able to perform precision tasks.
Standing allows the person to exert greater forces. Standing allows greater freedom of movement. Muscular stress in increased for people who stand. If you must stand, try to alternate with a seated task. First, determine your reach envelope - the reaching distance your body can handle without putting it in awkward positions.