its a popularity contest. essentially when you launch, you want to get everyone that has ever used your product to upvote. generally, ask people to leave feedback on the ph page
ph has a very lopsided outcome distribution - either you make the top 5 in your day or your never seen from again
if you launch at the beginning of the week you have better chances of being top pick of the week which gives you another bump
ph crowd likes having special treatment - eg. discount codes or other things for ph people