Here are some tips that can help you with this:
Emotional Intelligence Training: Developing emotional intelligence skills will help you better understand other people's feelings and emotions. This can help you notice subconscious cues and subtle signs.
Active listening: Listen carefully to what people say and pay attention to their tone of voice, facial expressions, gestures and manner of communication. Often, "red flags" can manifest themselves in nonverbal communication.
Ask questions: Asking questions can help clarify information and better understand the person. This may also help identify inconsistencies in his story or behavior.
Trust your intuition: If you have feelings or hunches about a person's behavior or character, do not ignore them. Intuition is often an important tool in recognizing red flags.
Studying Psychology and Behavior: Studying psychology and human behavior can help you better understand the motives and actions of other people. Knowing the basics of psychology can help you analyze behavior and character more successfully.
Be vigilant: It is important to remain vigilant and not ignore warning signs, especially in important areas of life such as personal relationships, business transactions or finances.
Remember that the ability to recognize red flags in other people develops with time and experience. It is important to approach this process with respect for others and not jump to conclusions.