What does a beginner look at first when a stock gaps up at the open?

I keep seeing posts about stocks that open much higher or lower than where they closed the day before. People say it happened "on the news," but I'm not sure how to tell what actually matters. I don't want to guess. From what I've read, a gap is just the difference between one close and the next open. Some people say they check whether there was any news overnight, how big the gap is compared with a normal day, and how heavily the stock traded in the first few minutes. I'm not sure which of those is most useful, or whether there's a simple order to check them in. Could someone explain what they personally check first, and why it comes before the other things? I'd like to understand the process, even if I'm not sure yet how much weight each part should get.