How does one make roms?

Im wondering so I can make my own from my stuff. What do you need to: Get bios images from your unit? Get roms from your cartridges? Get it all to work?
from what i've seen, you plug a device into your system, and then the game into that. you can then hook that device to PC...

its not something a lot of people have. it goes for hundreds of $$$....

why would you want to make roms of stuff? *everything* is out there already.
get a dumper

dump rom

the most well-known (reliable) source would be lik-sang, although they are tad expensive there, and they love to rip you off

but i agree with xeno... unless you plan on ripping something no one has ever dumped before, like one of them limited edition carts or something, it's better to get what's "out there already," assuming you already own (in physical form) whatever rom you plan on getting..