You must have a complete methodology for investing in IPOs. And, you must do it in a way that puts the odds in your favor.
Just deciding on 5 random IPOs that you 'believe' will be good, isn't good enough IMO. A good company or good technology does not make a good stock. Do you realize that most of the big-name IPOs these days are the inside investors cashing in? They are not raising money so that they can invest in the business. They are paying off all the seed investors, founders and private equity guys. And the public gets stuck with the bill. With things like SecondMarket, the shares could have changed hands several times before they get to you. Very easily you could be the greatest fool buying on IPO day.
You will have to view each IPO you buy as completely random. It could go up or down, or sideways, and you really have no idea which one it's going to be. Just buying 5 companies is not enough diversification. They could all go to zero. Professional traders and gamblers will hardly ever risk more than 1-2 percent of their account on any one stock/trade/poker hand etc. This is because risking any more than that could easily blow up their account. Suppose you are right on 50% of the IPOs that you buy. Even though in the end you are right half the time, you still may have a string of 10 or 20 losers in a row. What if you risked 10% on each stock and lost 10 times in a row? You'd be broke.
A complete trading system that buys IPOs would go something like this:
1) Use the high of the IPO day as the trigger
2) Buy the stock when it closes above the high of the IPO day
3) Subtract 10% from the high of the IPO day price as the 'stoploss'
4) The distance between the entry point (IPO day high) and the stop loss is the risk
5) Risk no more than 1% of account equity on any 1 IPO
6) If not stopped out, sell IPO when it closes below the 200 day moving average
So, if the high of the IPO day is $10, then your initial stop loss would be $9. With a $50,000 account, you would risk $500 on each trade. The distance between $10 and $9 is $1. $500 divided by $1 is 500. You would buy 500 shares of the IPO at $10. This means you're actually buying $5000 worth of stock, but your RISK is $500 because you are gonna sell if it drops more than $1 a share. If the IPO goes up to $50, congrats you just made $20k. That just paid for 40 losing trades. You could also have quite a few losing trades in a row. Most likely you would give up after about 5 losing trades in a row. This is not for the faint of heart. Don't ever risk more than 10% of your savings on speculative stuff like this. Unless you are a professional trader, you'll probably lose money. If you end up making any money, it's probably because you got lucky. Professional traders work very hard at this kind of stuff. Don't expect that you'll make anything from 'playing around,' but good luck anyways.