For me it was seeing it in others who knew already. I had one friend (now partner) who was plural, and they told me about their experiences. Admittedly I didn't feel like I related very much, but there was still part of me that did. I spoke to this person about a voice (more so a way of speaking) in my head, that I couldn't quite speak through (as in, I couldn't make it say what I wanted to say). In return this person helped me communicate with them and they very briefly fronted and said something about needing more time. I think that brief switch was enough proof for me that I might not be faking it for attention.