The first half hour of the US markets are great for trading, but only if you know what you're doing, and are quick on the buttons! They are lethal otherwise. So practice and practice before you dip your toe in the water.
Some days are much easier to trade than others - have a look at the overnight trading to see if there are any clues as to overnight support and resistance.
From having traded the opening bar, my observation is that the market often (but not always, of course) changes direction on the third 5 minute bar. So if I enter on the first bar, I would be looking to take my profit on the second or third bar, and anticipate a possible change in direction.
Trading the opening is often just a continuation of the previous day's activity (ignoring the overnight stuff). So if the previous day had one big drop during the late afternoon, then you would expect to see some consolidation (triangle, flag, etc) at the opening. This is just basic TA knowledge of Elliott Wave formations in trends, and pullbacks. If the previous day had a wave 1, wave 2, then a wave 3, you would obviously expect the day to open with a choppy wave 4 - great to avoid, unless you know what you're doing.
The overnight trading will tell you if there is going to be a gap formed at the open. You probably have your own gap strategies, but on such days I would take my profit on the first and second bars, and be ready for the turn on the third. If it doesn't turn properly on the third (ie not a trend reversal, but just a little pullback), then the market is often already in its trend for the first hour or two of the day.