Here's my probably unhelpful opinion to this old topic that has suddenly caught my attention
Don't outright state it.
"Yup I'm gay and proud!!" No one wants to say that to a stranger ya know?
I prefer when writers suggest it. My main character is pansexual I guess (I don't get all these names). He doesn't really mind anything. Two romantic interests he has are female because that's his ultimate preference but sometimes he does get a but flustered when he encounters an attractive male.
Eve: The Awakening by Jenna Moreci has a gay character but it's revealed in subtle hints. Like in conversation his friends mention a past crush or partner. Don't remember exactly but it's obvious but hasn't been stated.
It comes down to a healthy balance of relevance and representation. I have very few strictly heterosexual characters; but many times, their sexuality is understood through character development that progresses through a story, and how they interact with other characters. It's like others have mentioned; hinting is a good form. Outright stating, unless plot-relevant, doesn't always help. It's the finer details that make a character A+ and I think that extends to their sexuality. I find this particularly useful for characters that extend beyond the basic LGBT spectrum.
It isn't always necessarily important to the story, but if you drop subtle hints at their sexual preference, readers may pick up what they are. I have never explicitly said that my character was heterosexual, but with how he behaves around women, I've made it to where I don't have to say it.
