Anytime that I meet person to person with a new (new to me) trans person I tactfully ask them leading questions to access whether they are trans. For instance, if they are a strictly crossdresser that is only dressing as a fetish and acknowledges that they are male then I don’t want to establish a relationship with them because they are usually looking for a physical relationship and I am not interested. This does not include the person that thinks they are female but unable to transition at that time but still dresses as female at every opportunity. Nothing personal but I am not interested.
If someone tells me they are trans I will tactfully ask them to tell me their trans story. If I determine that a trans person has a female heart and soul I can sense it through their answers. And then they will have my complete acceptance and support until such time as they prove they are not worthy of it. I never pass judgement on someone I have just met based on appearances.