Check with your last base. If you didn't separate too long ago, there is a chance that the military separations section of your old base may have a digital copy of your DD 214. It is best to go in person and make the request rather than to do it by phone.
Look at the last place of residence you put on record. Many veterans forget to change their place of residence, which can be different from where they started their career. Your copy of your DD 214 could have been mailed there if the address change wasn't made.
Research the VA Regional Office for a copy of your DD 214 if you filed a medical claim within the past five years. You can't even register into their system until you have a DD 214.
Log onto the Veteran Records website (see Resources). Follow instructions on how to get your DD 214. The instructions do include faxing or mailing forms that require your signature and your Social Security number. They have to be received within 20 days of the request, so don't delay.