Eh except in specific circumstances there's no reason to mention the sexuality of a character; how often do authors point out that their characters are heterosexual? Never, people just assume so and their assumption is often confirmed by the character's actions.

I think it's much better to write gay characters same as any other; it's just instead of pursuing the opposite sex, they'll pursue the same. Pretty simple.

Just like in real life where I only mention that I'm gay if it's relevant to the conversation, it should be the same in media: for example known characters in a later chapter discussing a plan to get their friend, someone they just met, a date. Interrupted by one character in the group who has known said friend for longer, laughing at the others' suggestions of partners and exclaiming, "this won't work!" she exclaims, "but why?" they ask, "she's a perfect match" "but he's gay!" she laughs, "but if she has a brother..."