Borrowed from notes made at http://dryicezero.blogspot.com/ and elsewhere; copied here because at least one site has disappeared its local copy!
On older systems you may need to manually set some module parameters etc. This doesn't seem to have been necessary since Ubuntu Dapper Drake at least, possibly earlier.
# modprobe usbserial vendor=0x1199 product=0x0112 # mknod /dev/ttyUSB0 c 188 0
For PPP to work, you'll need to create two files:
lcp-echo-interval 0 ttyUSB0 115200 debug noauth defaultroute usepeerdns user USERNAME show-password crtscts lock connect '/usr/sbin/chat -v -t3 -f /etc/chatscripts/1xevdo'
'' 'AT' 'OK' 'ATE0V1&F&D2&C1&C2S0=0' 'OK' 'ATE0V1' 'OK' 'ATS7=60' 'OK' 'ATDT#777'
You'll also need to stick your username and password in /etc/ppp/pap-secrets. Make sure to update USERNAME in /etc/ppp/peers/1xevdo as well.
echo "mobile@jamamobile * telecom * >> /etc/ppp/pap-secrets"