Couple of things to look for.
Check out the car park, what state are the ordinary workers cars in, and compare to those of the managers, if possible.
If the cars are mobile wrecks then I’d leave that place alone.
Do the staff work lots of overtime and is it paid ? Office staff are prone to being required to do lots of unpaid overtime - work is worth money, time is money if they wont pay then screw them.
Is everyone is grabbing the overtime, is it because they need the money ?
Does the company employ lots of the type of peole who would have a hard time getting employment elsewhere, such as the badly educated, immigrants, those who are nearing retirement age ? I’ve found companies like this are usually not doing it out of social concern, rather these people are easier to exploit.
What is the attitude to health and safety, is the job more important than employees health ? Even in office environments there can be hazards such as fire routes compromised, office desks crowding doorways because the place isnt big enough(which is a red flag to me) Poor heating or lighting are other reasons to walk away as these are signs of lack of concern for staff.
Do they enforce health and safety despite it perhaps being inconvenient to employees, things like safety hats, eye protection, steel toed safety boots, if they are supposed to be using them and the company does not enforce it you can reasonably say that this company is ony interested in defraying liability and is not actualy interested wether you live or die.
Look at the average age of employees and length of time worked there, good jobs dont come up as often as bad ones - for obvious reasons.
Do any of the staff have paid time off to study, such as apprenticeships, or other career enhancing studies, and what is the company policy on external staff training, just about all companies have some form of minimal in house traing such as fire drills, or minimum legal obligations.
If the company fulfils minmum legal obligations and goes no further, leave that company behind.
I have seen companies that actually discourage staff from gaining other qualifications because they reason that better trained stafff are more likely to look for better employment elswhere.
Some companies use various testing procedures to discover what sort of person you are, I dont mean the handwriting shite here, I mean the kinds of tests to discover wether you are an outgoing person, wether you enjoy technology, whatever, the idea is to employ a person in a role that more or less matches the persons charactor, if nothing else it does show that the company is very concerned about the quality of its recruits and may well be prepared to invest in them.
Does the company have a personnel handbook, that is - a guide to the procedures for both you and the managers, it should lay down clearly things such as attendance, sick pay, holiday entitlements.
It should also state clearly what disciplinery procedures are, and what recourse both you and the company can take.
Does the company provide work clothing or provide an allowance, on the shop floor certain work clothes might be necessary, some companies provide overalls and ensure that they are cleaned.
You know what you can do for the company, you will contribute to its smooth running and in some way you will make money for it, perhaps be part of someone elses career progression, but what do you want from the company, will it allow you to grow, change roles, perhaps take a completely unexpected career path?