Try to avoid buying the mailers that are padded with paper fiber. Some traders feel that these can contaminate the CDs with small particles, especially since the packages seem to easily get statically charged and can rip when opening. Jewel Cases will usually not survive the shipping, and add significantly to the postage costs. So take the required number of discs and place them into either clamshells or Tyvek sleeves. I got mine from American-Digital .
Clamshells provide better protection, but increase the postage cost.
Most people find that sleeves work fine. Put an address label on the bubble mailer, to reflect that it will be coming FROM the trader TO you. Be sure to use a return address where this mailer can be delivered to you. Put the discs into the Bubble Mailer. Be sure to mention how happy you are that this kind person is willing to do this for you.