摸着石头过河

摸着石头过河

Literally means:

wade across the river by feeling for stones on the riverbed

Actually means:

learn how to do something through trial and error

It figuratively means one tries doing something in the process of which he gathers experience and finds the effective way. It refers to things that have not been tried before and thus one has no model to follow.

比喻先试着把事情干起来，再在干的过程中总结经验教训，找到有效的方法。所做的事一般都是前人没做过的，没有前例可以借鉴。