When meeting and having a ts dating, if you are not sure their pronouns or gender identity, the best way is to ask them directly. Sometime, it may be awkward to ask them directly, especially in public places, but it is better than misgender transgender people and call them with incorrect pronouns. Be different from ordinary people, many transgender people may used to be asked this questions. Instead of being misgendered, they prefer to answer questions about their gender identity. Sometime, this can be a great way to make friends with transgender people. As a straight person, you ask about their gender identity before talking with with, it shows you are respect their gender identities. It is hard for transgender people to meet people who can understand their gender identities, so they are willing to make friends with you.
In lgbt community, misgendering is seens as an insult. Becuase transgender people often be characterized in a way they don't want to be be. They are often misgendered as gay, female or male. What's worse, some opponents of transgender even don't respect transgender people and treat them as a special community. It's okay of they cannot understand the gender identity of transgender people, but every should be respected. These unfriendly people are not welcomed by transgender community. Transgender people are very sensitive when communicate with other people, some subtle acts may affect them. So if you want to have a long-term relationship with them, show your respect to them when you first meet each other. Your understanding and disrespect to them may ruin a relationship. This is why I always mention you should be friendly to transgender people you meet.
Let's imagine that we live in the same world the same society, we to through the same thing everyday. We need to interact with other people in everyday life, it seems normal for everyone of us, while it is not always easy for transgender people. Before making friends with a new person, they need to consider about many problems, sucha s if it is safe to date a stranger, how to tell other people that they are trans. For both transgender people and ordinary people, transgender dating relationship is hard to deal with.
Everyone in transgender community have tried to find the right pronoun for themselves, while everyone's understanding on pronouns is different from each other. So the polite way to ask transgender people about their gender identity and pronouns is ask them directly.