+1. Headshaver here as well and Jimbo's video really helped me. I'm not sure if it helped more in technique or motivation, though.
Definitely get your face down pat before trying the head. I still need to see where I'm going in the back so I use two mirrors when shaving the back of my head. I usually go 3 or 4 days between shaves and use a shower, conditioner and jojobo oil as part of my preshave routine.
My best advice would be to keep a styptic handy, especially when starting, as head nicks/weepers will bleed a little more than ones on your face.