shouldn't be kept ground for a long time. It's recommended to grind them with the help of special mill or pound in mortar just before using for food.
Leaves of vegetables should be also torn off before using. You may keep them in refrigerator, as well as in a glass with water, if you want to preserve them fresh (but only for a short period of time).
Don't pour spices in a pan with boiling broth directly from a jar where you keep them, cause they absorb moisture from vapour and lose their quality.
If you want to use for cooking of one dish several kinds of spices, which are kept in grains, you should grind them so that they have the same size of grain.

So, here are the main tips of right keeping of spices, which are in fact are quite simple to follow. But many people forget about or sometimes even don't know these rules and their spices get out of order very quickly, losing initial aroma and taste. Hope you are going to avoid it!