Constantly recycled job openings - to spot this you need to be searching for a few months. But if you notice that the same posting is ALWAYS up for senior positions, and it's not a huge company, your resume has a huge chance of never being seen. From my experience, it's likely a company fishing for H1B applicants. Even if you're on a visa stay away.
No intern program - as a general rule, companies with best engineers scoop many straight out of school. I have never worked at a company with top notch engineering that didn't have an intern program. Sometimes this is hard to see since they focus on certain schools, you may be able to find out from recruiters or Glassdoor.
Heavy usage of third party recruiters - the best jobs are easy to advertise. Either the company is incompetent, the position is for legacy work, or the company is just unnapealing in other ways. If legacy work is your jam, go for it, otherwise be cautious. Note that this does not apply for specialized or very high level positions. Use of executive recruiters is normal since paying the cut is worthwhile.
Low or no bonus - we're in a tech boom nearing 90's levels. Your bonus should be 10-30% of your salary. If the company is public, you need stocks. This is the primary way companies keep apparent wages low. The golden eggs are hidden in bonuses, perks, generous vacation policies, and especially public company stock.
Old school practices - occasional work from home, somewhat flexible hours, casual work environment, free snacks. If they offer less than 3/4 you can find a better gig.
Non technical management - this should speak for itself. I've done it before to much regret.
Strange hiring practices - personality tests, panel interviews, minimum GPA rules, leetcode, asking about personal life (married? Kids? Political views?). If you like the idea of hanging out with people from MENSA, sitting in countless committee style meetings, or next to some frat bros or guys wearing MAGA hats maybe this is for you. But asking these things of you reflects the values of the organization. Birds of a feather flock together and humans are no different.
Find a place with engineers that seem to love what they're doing, eachother, and writing code. If they invite you to lunch and everyone is chatting like old friends you probably can't go wrong. Bonus if they're actually excited to talk to you about technology and what they work on.
There's much more but I'm sure the comment section will be flooded with it :)