How should I package my seeds?
Seeds should be packaged in a manner to protect them from excessive light, heat, and moisture, any of which can damage seeds. If you're planning to collect only a few seeds, you may prefer to use what you have on hand for packaging: various types/sizes of paper envelopes; the cut off corners of envelopes, folded over and taped shut; a sheet of paper folded into a packet and taped; tea bag wrappers; recycled, relabeled commercial seed packets, etc. Be careful when taping up such containers as small seeds can either fall through tiny openings or become permanently attached to the tape itself. Avoid plastic sandwich bags which are generally too large for seed storage and can tear easily.
If you plan on lots of seed collecting and trading, there are several good, commercially available containers, including small, clear plastic zip bags (craft stores, hardware stores, electronic parts stores); paper coin envelopes (stationery and office supply stores); and glassine envelopes (stamp and coin collecting suppliers, some craft and art stores).
There are advantages and disadvantages to each of these. Plastic bags allow easy viewing of the seeds but offer no protection from light and will absorb any available heat. They close securely and are moisture proof but will retain moisture if seeds aren't dried adequately (a few grains of dry rice with the seeds helps prevent mildew); they are slippery to handle and difficult to write on; and they offer little cushioning to the seeds they contain.
Paper coin envelopes close securely but cannot be opened and reclosed easily and may 'leak' small seeds at the corners (tape all corners to prevent this). They are light proof; allow for a certain amount of air circulation but are not moisture proof; are easy to label, write on and handle; and offer some cushioning to seeds.
Glassine envelopes are barely adequate by themselves (tear very easily, etc.) but are good containers for very small seeds when used in combination with an outer envelope.