Tar backup question

I have my system back up now and want to back it up. I would like to backup the full disk with tar except for the /tmp /media /proc /dev directories to a usb drive /media/SEAGATE. Could someone please write me the EXACT sytax to do this? The last time I tried this, I ended up filling up the disk I was backing up with nothing on the /media/SEAGATE drive even though I though I was following the help on tar I found on the internet. Art