Mist Moons
get a tissue, pinch your nose and tilt your head up, then lay on the bed waiting for it to stop. (pinch softly)
if it's really heavy, take a tissue and make a kinda medium sized ball shape and stuff it in your nose. take it out in 30 minutes
sweatdrop
NO. Tilt your head DOWN. And don't lie down. Otherwise all the blood will go down your throat. As well as being horribly unpleasent, swallowing it can lead to puking.
When you have one, just pinch the fleshy bit of your nose, tilt your head foward, and wait for it to stop.
Only advice I have on preventing them is to use soft tissues and not blow your nose too hard. Google says the vaseline thing helps.