To guarantee that you are using fresh spices, buy them in small quantities and date them. Replace old spices once a year. For suggestions on how to substitute spices, use the Spice Alternative Guide.
Spice Alternative Guide
Whether you're making an emergency substitution or experimenting with a new flavor, follow these suggestions for spice alternatives. As a general rule, start with half of the amount the recipe calls for (unless directed otherwise), and add the spice till it suits your taste.
Allspice: cinnamon; dash nutmeg; or dash cloves
Aniseed: fennel seed or a few drops anise extract
Chili Powder: dash bottled hot pepper sauce plus a combination of oregano and cumin
Cinnamon: nutmeg or allspice (use only 1/4 of the amount)
Cloves: allspice; cinnamon; or nutmeg
Cumin: chili powder
Ginger: allspice; cinnamon; mace; or nutmeg
Mace: allspice; cinnamon; ginger; or nutmeg
Nutmeg: cinnamon; ginger; or mace
Saffron: dash turmeric (for color)
Q: How can you tell if a spice is fresh?
A: Judge the freshness by the color and aroma. When fresh, most spices have a bright, rich color and a strong aroma when you open the container. If either the color or the aroma seems weak, replace the spice.
Spices will keep their flavor longer if they're stored in a cool, dry place. Keep them tightly covered because exposure to the air accelerates flavor loss. Whole spices stay fresh up to 2 years and ground spices about 6 months.