I ignore the Greeks. I do not use them at all. I use Probability ITM which displays on my trading screen instead. Before that, though, I try to gauge market sentiment and depth base on the pre-market in futures activity, which is almost entirely seat-of-the-pants. Using that I assume a trading range of between $40 to $60 either side of the open. Using my Trading View chart, I look at past sessions for support and resistance levels and set alerts for those to give me a visual. These, BTW, more often than not are about one strike wider than the standard deviation indicated on my trading screen's option chain, and then I wait for the open.
After the bell, I watch the chart for the action for, usually, between 30 minutes to an hour. If it is choppy I wait even longer for things to settle. If/when it smooths out and resistance and support begin to become apparent I start looking at the option chain for an opening trade. While I'd love to get $1.00 or more for $400 or less of buying power with an 85% POP, that just doesn't ever happen. But I'm willing to accept $.65 while using around $400 so long as the POP% is around 72% or better. It takes me 15 or 20 minutes to execute a trade because I am trying to avoid the kind of mistake I made today. BTW, my initial trade setups have been correct 100% of the time. All of the adjustments I've made, especially the one today, have been redundant and expensive. I am NOT a genius. I'm just really careful, MOST of the time.