If you're trying to determine someone's gender identity, it's important to remember that gender identity is a deeply personal and individual experience. It is not always possible or appropriate to know someone's gender identity just by looking at them. Some people may not conform to traditional gender norms or may identify as non-binary, genderqueer, genderfluid, or transgender, among other identities.
The best approach is to treat everyone with respect and use the name and pronouns they have shared with you. If you are unsure about someone's gender identity, it's perfectly okay to ask politely and respectfully, as long as you are prepared to accept and honor the response they provide. If they prefer not to share or if it's not relevant to your relationship, that should also be respected.
Remember, gender identity is about how someone feels and identifies internally and may not necessarily align with their physical appearance or the gender assigned to them at birth. It's essential to be understanding, open-minded, and respectful of each person's unique experiences and identities. Focus on building meaningful connections and treating others with kindness and empathy.