Dry your seeds on the vine after harvesting your vegetables. Save your seeds from the healthiest plants. Seeds inside vegetables, such as cucumbers, must be left on the vine to mature. The cucumbers you pick to won't have mature seeds yet.
Check seeds for maturity. Most white seeds become cream colored and brownish seeds will turn dark brown. Harvest your seeds only after they have turned the proper shade. Cover the plants with netting to keep birds and other animals from eating and gathering the seeds.
Pull back the husks of corn, garlic and onions to expose the seeds to the sun to dry them for seed harvesting. Peas, beans, herbs and carrots should be left on the plant as long as the weather will allow.
Spread your seeds over a screened frame to dry. For smaller seeds, tie a paper bag over the plant and hang it so the seeds drop as the plant dries. Place your seeds in a dry, ventilated location. Make sure it is safe from animals who might steal the seeds. As your seeds dry, remove any pods or debris.
Store your seeds in envelopes. Write the name of the seed and the year harvested on the envelope. Fill it with the seeds and seal it. Store the envelopes in a cool, dry location where they won't be bothered.