Love is love is love is love. While who your character loves isn’t necessarily who they are sexually attracted to (they could be be asexual and biromantic), who your character is sexually attracted (and who they romantically love) does affect who they are so it’s important to give actual consideration to who each of your characters are attracted to and what label they give that love. Don’t make all of your characters hetero because you are or because society is heteronormative. We’re heading toward a world where heteronormativity is no longer a thing, so don’t let your story become a relic of a less accepting time.

I apologize if the links below don’t provide a broad enough perspective, however it hopefully provides a jumping off point. As I find better resources for these lists, I will publish updates.

Fuck Yeah Character Development’s Writing the LGBT Community
Kelly J. Ford’s Beyond the Closet: Writing Gay Characters
Chloë Curran’s One Gay Character Isn’t Enough<
GLAAD’s Media Reference Guide – 9th Edition
GLAAD Media Reference Guide Lesbian / Gay / Bisexual Glossary Of Terms
Malinda Lo’s Avoiding LGBTQ Stereotypes in YA Fiction, Part 1: Major LGBTQ Stereotypes
Malinda Lo’s Writing about lesbians when you’re not a lesbian
Brit Mandelo’s Queering SFF: Writing Queer—Languages of Power