How should I store vermouth and other modifiers?

The answer

Keep opened vermouth in the refrigerator with the cap tightly closed, because it is a wine-based product that slowly loses freshness; try to finish a bottle within a few weeks. Spirits can stay on a shelf in a cool, dark place, standing upright. Fresh juice and homemade syrups belong in the refrigerator, and syrups are best used within about two weeks. Label homemade items with the date you made them.