It's hard enough to analyze the stock of an established company. An IPO company is even trickier to analyze since there won't be a lot of historical information. Your main source of data is the red herring prospectus, so make sure you examine this document carefully. Look for the usual information, but also pay special attention to the management team and how they plan to use the funds generated from the IPO.
And about the underwriters, too. Successful IPOs are typically supported by bigger brokerages that have the ability to promote a new issue well. Be more wary of smaller investment banks because they may be willing to underwrite any company.
It's important to understand that underwriters are salesmen. The whole underwriting process is intentionally hyped up to get as much attention as possible. Since IPOs only happen once for each company, they are often presented as "once in a lifetime" opportunities. Of course, some IPOs soar high and keep soaring. But many end up selling below their offering prices within the year. Don't buy a stock only because it's an IPO - do it because it's a good investment.