Always remember that you have to a forward view of a company. When buying, the foresight to see value when others look right past it is a critical attribute.
It is just like buying a fix-it-up home. You have to see "what can be done" when others turn away. You also have to have a seller who does not see the value. That's where your best deals will come from when buying equities, as well.
Micron Technologies (MU) had a trailing PE of 6 two years ago. Sales and earnings were moving up but not without pullbacks. A general understanding of the memory market provided the context to understand what the future could be.
Today MU came through with some robust revenue and earnings. Unfortunately. at this point, the market has already acknowledged the potential and the price reflects that fact.
Two points to bear in mind. First, open your eyes to what could be when opportunities to buy are cheap. Second, read as much as you can to understand the company, the industry and the economics of the business.
In this case, good things don't always come to those who wait!