Certainly follow momentum, but only if the underlying story makes sense. Many companies come to market prematurely. Their early share price price performance owes more to post flotation hype and restricted selling than intrinsic prospects. Pre-flotation investing can be lucrative if you're smart. Earlier stage is not necessarily less certain.
Many companies go public far too early.
If you invest in IPOs, you often pay for substance that has not yet been delivered. They should build a business before crystallising wealth by flipping to unsuspecting punters. And pre-flotation values are more realistic, because you're competing with professional investors rather than lunatics. Traditionally, such investments were chancy, but risk must be balanced against price. If you're taking a medium-term view, it's smarter to buy an illiquid stock at a sensible price than a quoted stock at an outrageous valuation.