There is a lot of talk about 'institutions' and 'big boys' but again, that is a myth. Are 'they' trading the open, sure, orders from the night prior come in but much of the order flow today is HFT controlled, or done via algorithms. Firms like Citadel facilitate large market order flow and it's not what you think with people on a floor anymore yelling and screaming, don't believe us? Watch a video of the Citadel trading floor here. So what does this do for us as discretionary, retail-traders? The truth is not much. You shouldn't be worried, what matters is what the price chart says.
Trading the opening bell is like anything else: Where are your price levels at and how is the market reacting? If SPY (or E-Mini S&P) is strong off the open you want to see your stocks (that you're long) move right with it. If they do not, something is up and you should take notice. That's lesson number one.
If the market opens and is strong, then you want to analyze your levels and begin to scale out of your positions. There is nothing worse than being right on a trade and selling it early only to see it trade higher throughout the day.
Usually the market will slow down at about 11:30 am EST, the European close. So the first 2-2.5 hours are crucial for trading, in fact, that is really the open. Below is a live 14 minute video of trading the open on NFLX using a short term call position.