I like J. Allen
's approach, in crowd scenes then have same sex couples holding hands or embracing, just to show that it is as much a part of 'normal' life as a Ferengi trying to earn profit.
Portraying a gay character would be no different from a straight one in the Trek-verse (IMHO), all that would change would be on their obligatory 'relationship episode' the gender of the person who they fall for would be the same as themselves. Their sexuality doesn't need to have stories written especially for it.
In the Dax/Kahn episode (I think its called "Rejoined"), the focus of the episode was on the fact that they couldn't be together because they were both Joined, not because they were women.