Port, protocol and params for avrdude and Arduino

What is the right syntax of avrdude in order to download a hex file into an Arduino board?

I'm trying:

$ avrdude -B100 -v -C /etc/avrdude.conf -p m168 -c stk500 -P /dev/ttyUSB0 -U flash:w:~/arduino-0011/sketchbook/PWM/applet/PWMtoy.hex

But it says:

avrdude: stk500_getsync(): not in sync: resp=0x60
avrdude: stk500_2_ReceiveMessage(): timeout

If you set the following in your preferences.txt file you should see how the IDE calls avrdude on your computer when it uploads:

upload.verbose=true

--Phil.