Last night, I did a short(?) series of tweets discussing tips on how to write demisexual characters in your fiction. Those tweets have been storyfied here. WHOOHOO! The tweets focus on how to write demisexual protagonists, though it’s probably general enough to give you an idea on how to write any kind of demisexual. (That said, less screen space and no pov time makes it really hard to show a character as explicitly demisexual, so my recommendation would be that, if you want to include demi representation in your stories, make it a prominent character, so you have the space needed to explore how demisexuality works.)
And because I tend to write out longer tweet threads/storms like this before I start tweeting, here’s the original too. It’s slightly different at points because I do rephrase a little as I tweet, usually to allow for the character limit, but it’s effectively the same thing.
tl;dr best tip version: Let characters become firm friends first and then slowly layer in your demisexual character’s sexual attraction. Layer it. Also read the linked tumblr posts on how to avoid invalidating other ace spec sexualities and, when you’re looking for sensitivity readers don’t forget about the rest of the spectrum. Everyone will have something valuable to say about how you handle it!