I have spent a lot of time trying to learn how to be right on whether the market will go up or down the next morning. It's not doing me any favors because of "premarket" trading. I find a stock that I assume will go up and during premarket, it's already gone up as if everyone else has already beat me to it.

My question is, is better to get in during trading hours? And I am having the hardest time grasping the concept of people being able to measure risk.

I see some traders that already know whether that stock will go up or down. Fabulous, I assume they figure it out during trading hours to get a good position.
What I don't understand is how someone is able to predict, okay this is a reversal, we're at X number, it will climb 10 cents from here. That's extremely precise, how do you base something like that?

Through the stock history, through an indicator, through volume, through the news?