My red flags were pretty straight forward.
Would never continue dating someone who doesn't put out by the third date and doesn't fuck really well. First fuck better be a weekend long sweat fest. No dead fish. No ridiculous vanilla level limits. No party poopers. No bigoted intolerance. Respect me. If you don't accept your punishments, then your ass is gone. Must have a car, job, and not live with their parents.
No one got past the third date if they were not long term material ... still managed to have 2 - 3 dates per week whenever I was single.