How to think about a company's value

I knew how to assign value to a pack of chips so do most of us, then I'd more recently learnt how to have a keen eye in valuing property, but companies, they're huge, some you don't see them around but for their ads and others not at all, I quickly learnt that valuing them would an important skill I'd need to learn properly. 

I saw that stocks I'd watched over the years had up and down swings, and factoring in a bit of inflation, I'd know based on whatever vague knowledge the news allowed me to gather on the company and it's past stock movement whether it was cheap enough to buy. 

With the complexity of a corporation being able to know when it's at a discount is important and also knowing when it's too high, because as it's shown many times people are paying the future price for something now, then the best case scenario is that the company realises it's planned goal and the earnings match it in future, but you don't gain because you bought at the top, when the price was high simply because everyone believed in the company. Knowing when to buy can make all the difference.