Stay out. Investment bankers (henceforth, "eye-wankers") underprice IPOs as a way of skimming money into the paws of their scumbag clients, but if you're not well-connected in scummy circles and therefore can't get allocated into the IPO, then by the time you can purchase the stock (not participating in the IPO, but trading on the open market in the following day) this opportunity has vanished.

IPOs are a disaster for ordinary investors. If the IPO's good, banks will reduce your allocation to let important clients in. If it's a dud, they'll let you get in as deep as you want. So you face adverse selection.

Also, definitely do not make a market order on the day of an IPO.