Datasheets are your friend. They tell you which leg is positive, which is negative, what the expected voltage is, how big the package is, etc. You can find a lot of datasheets by searching for the part on Octopart or just even googling the part number.
The bins in 016 sometimes aren't labelled well enough for you to be able to look up the part number. However, if you find a bin labelled 'electret microphones' in 016, you can be pretty sure that they are the kind that is listed in the Fab Inventory.