In the job description
The applicant should be wary if a very wide technology stack is specified in the job requirements. For example, an excellent knowledge of four or more programming languages at once should confuse the applicant. Or if contradictory to each other, as well as “vague” official duties are indicated. Almost always, the demand of a "jack of all trades" or enikeyshchik does not bode well.
In an interview
A situation should be alerted in which a potential manager cannot clearly describe future tasks, and if the interviewers themselves are poorly oriented in the project that they are looking for an employee. It’s worth thinking twice if you see that the technical interview is superficial, the interviewers themselves do not know the correct answers to their own questions, and they make an offer after the first meeting.
If possible, evaluate the general atmosphere in the company if you are invited to openpace, where 5 people silently and sadly work, while in an interview they say that the company has a “vigorous scrum”, you should be wary.
A separate issue with startups is if you are interviewing in such a company, take a little interest in the business: who invests in the project and whether it has reached self-sufficiency, what are the prospects for the product, etc.
Feel free to ask questions regarding salary. An alarming call can be, for example, a situation in which you are offered the so-called “gray salary”. Or if it is discovered that 40% of the salary is quarterly bonuses that depend on the results, but the company cannot clearly indicate what these results should be, and even more so are not ready to fix them in the contract.