Be sure the seeds you buy are fresh; they should be dated for the current year. For many plants, seed may be sold in three different forms: loose, pelletized, and in tapes. Loose seeds, traditionally sold in packets, are familiar to all gardeners. Pelletized seeds, also sold in packets, are individually coated (like small pills) to make handling and proper spacing easier. Seed tapes are strips of biodegradable paper with seeds embedded in them, properly spaced for growing to maturity. You just unroll the tape in a prepared furrow and cover it with soil.
Store extra seeds in an airtight jar or other container in a cool, dry place. With proper storage, many kinds of seeds remain viable for a year, and some stay good for several years.