well, i fallowed the CUPS quick start guide at linuxprinting.org and got my printer going to the point where I can print a test page by going to http://localhost:631/printers/ and clicking the "print test page" button under my printer.

but when I click the print button in mozilla or openoffice.org's swriter nothing hapens. when i click on print properties in mozilla it gives this for the printing command
"lpr ${MOZ_PRINTER_NAME:+'-P'}${MOZ_PRINTER_NAME}"
but I dont know where those properties are stored or even what to set them to.

heres what localhost:631/printers says about my printer

based on that what should I set those mozilla varriables to? (and how/where do i set them)
also, if i wanted to print a text file in the command line, what would i type? (i think its "lp" but i dont know what arguements to use)

If your printer works correctly from cups you need only execute:
lpoptions -d <name_of_your_printer>

in your case: lpoptions -d deskjet3420

this command create .lpoptions file and all cups client will be using this printer like default.

If your mozilla still will be not print, this means that probably 'lpr' command which is executing
by mozilla is not from cups but for example form lpRNG system.
Solution for this is check or you have lpr.cups binary and if is like this replace 'lpr'. Or more save
create link lpr.cups to for example /usr/local/bin and then set in your PATH variable this dir on the top.
For example edit your .bashrc and put
export PATH=/usr/local/bin:$PATH

should works :> Generally if you can print from CUPS you need only check your 'lpr'

regards :>
b.