I shaved my head once or twice, and the best way for me to do this was
1) cut your hair REALLY short with an automatic razor.
2) then use normal shaving foam and put all over your head
3) I always shaved against the grain of the hair, think it gets cleaner that way, so i don't have do go ove rit more than once, but you gotta be carefull though.
4) Use some neutral cream that soothes your skin, e.g. nivea. (nothing with lots of perfume or alcohol in it)
I usually used the non-disposable gillete razor, wouldn't wanna try it with a disposable one...