Garlic
Clearly, any cook worth his or her salt needs garlic. Me, I prefer the pungent versatility of fresh, but if you're cooking for one or don't like your aromatics quite so aromatic, garlic power works just fine too, and is easier to control. Fresh garlic should be stored in a loosely covered container or in a brown paper bag. If it gets brown or starts to sprout, throw it out.

Ginger
It ranks with cinnamon as a must-have. In dried, ground form, it's warm, tangy, and comforting; as a freshly grated root, it'll clear your sinuses. Generally, you won't want to substitute fresh for ground or vice versa; it'd be a little like substituting your grandma for, say, Christina Aguilera.

Mustard
Clearly, if it's got a condiment named after it, it's useful enough to be in your pantry. Skip the seeds and go straight to ground. It's lovely added to any mayonnaise-based salads, and also works well in meat marinades. Later, if you're planning on adding pickling or corning to your culinary repertoire, you might want to invest in mustard seeds as well.

Nutmeg
This warm little friend ranks with cinnamon and ginger in the triumvirate of baking spices. Without these three there'd be no spice cookies, no pumpkin pie and no gingerbread. Purists say you should buy whole nutmeg and grate as you go. Lazy cooks like me just go with ground. The flavor may remind you of carnation flowers.

Bright Idea: Fresh ginger root may seem daunting, but it's worth it. You can pick up a root in the produce department of your friendly, neighborhood grocery store. Peel it with a vegetable peeler, and store it in the fridge in a jar of cooking sherry. That way, it'll stay moist and fresh, ready for grating. When you're ready to use it, just fish out your root, grate it with a cheese grater, and you're good to go. As an added bonus, the sherry in your jar will pick up the ginger flavor, and can be added to other recipes that call for wine.