At the risk of sounding like a smartass, you will know you will have correct bios when the games work?
. I learned everything i know from trial and error.
Seriously though googling will aslo probably give you the response you are looking for (or diff sets of neogeo bios to try).
Clrmamepro is another option (google for site and tutorial). I used to be afraid of it, but its really easy to learn following a decent tutorial. Basically it takes something called a dat file (also google), and will tell you speciffically whether a rom will work or not depeding on what version of emulator you are using.
Eg. what may work for mamedox, may not necessarily work for fbaxxx, or a mame you might be running on your comp.
If you are using fbaxxx just head over to their site for yet another easy solution. Fbaxxx is a much better emu for neo geo anyway. Need help running/setting it up? -all the info is there (and here for that matter too)
(somebody jump in here at any time here, as I'm not that great at explaining these things)
Good luck, enjoy the reading!