Here are the steps that you need to reset your password:
Level 3 Reset (Hard Reset)
1) Power on the device
2) Remove the back cover
3) Press and hold the small Reset button on the back for 10-15 seconds (you need a paper clip)
a. You should see the LED indicator turn yellow
b. The E-Ink display should flash all icons then reset when its ready
4) Release the Reset button
5) Restore the back cover
6) Allow the device to finish resetting and stabilize
When the device has been reset then you can refer to the default password which has been placed on a sticker on the back cover. If you lost that sticker and do not have it written down anywhere then you will have to contact Verizon.
And remember, you are not typing on a mainframe. Please don't shout everything you say by typing in CAPS.
I NEED TO KNOW HOW TO RESET OR RETIRVE MY PASSWORD. LOST PASSWORD FOR MY MI FI CARD?
There is a little hole just above the battery door on the back of the MiFi 2200.
Pressing a paperclip there for five seconds will force it back to factory defaults.
After that, the default WiFi password is the ESN-DEC found under the battery.
I should clarify that my response was directed towards the MiFi 4510L.
After reading ClarDold's solution I noticed that the default Wireless Password is located on the inside of the device as well. For the MiFi 4510L you should use the IMEI entry without any dashes. The last character does not appear to be necessary either.
For example if you IMEI value is 88888888-666666-1, your Wireless Password will be 88888888666666.