Hold a beer bottle out horizontally down where ur package is, then have a girl (or guy if ur into that) get down on their knees. Then open the bottle and have them drink it. It will resemble the act of giving head. Hence the name "Beer head." I guess you could shake it up first and try to get it to spray all over them if you wanted. The possiblities are endless. enjoy!
"who wants to give me beer head?"
"haha yeah dude that was awsome, she gave you beer head"