I could write a book on my experiences with this topic. It would be much easier if you had a specific person in mind.
I will tell you the most extreme time for me. I did not do it on purpose, so I am unsure whether I could replicate it with any sincerity. However, I fell in love with someone I was dating but never told. She had of course known some gay people, but had ZERO clue about what being trans was. We had been at it hot and heavy for a while and she wondered why I never let her give me any pleasure nor did I have sex with her. I just did things to her and I got down to boxers. Obviously I had to tell her at some point so I bit the bullet. I was so nervous bc I had zero idea how she was going to react. But I basically spent 2 hours telling her I had to tell her something about me that would probably change how she felt about me and that she would not love me anymore if she knew and so on. I was being sincere when I said all of this, and bumbling like an idiot. There was so much build up to what this horrible thing I had to tell her was- when I finally spit it out she was relieved. She was like Oh my God is that it? Who cares? Wow you had me thinking you were a child molester or something.
Now I do not recommend this approach necessarily but it worked out great in that situation.
I typically try to feel people out on at least the topic of anything LGBT related & gauge their reactions. I personally would not date anyone who was homophobic anyways so its doubly helpful to weed out those people. It is easy to get on the topic of politics to feel someone out.
I have also just spit it out over drinks. Women tend to take things a little bit more light hearted with a buzz.
I can go on and on about the hundred times I have had to tell someone. Most people will tell you the earlier the better. That is not my experience necessarily. For me it is nice for someone to know me a little before making judgments on me based on things they likely do not know much about. Plus I do not want to be seen as that "trans guy".. when someone gets to know me as Nick, the individual, then being trans is just something incidental about me.
If any woman ever gives you static- tell her the pros to your penis (no disease, pregnancy, stay hard as long as she wants, be as big as she wants, whatever size shape color). The one time a woman said to me "Why would someone want to date you and not just a normal man?" I spit out that unrehearsed speech and she changed her tune and propositioned me.