I'm going to jump in here and add that during interviews, there are all sorts of questions that we used to ask which weren't technically illegal to pose to a job applicant, but were asked to allow them to 'give themselves away' about information that we couldn't ask. It's been a while since I was a manager, so maybe others can chime in to this practice if it's still being done. A big one was to just ask what reasons the applicant might have for not being able to come to work. Acceptable answers might of course include death of a family member, illness or injury of same, illness of self, transportation problem which would make it impossible to get to work, and I think you can come up with some others. However, we would get assorted answers which would tell us things that we couldn't have asked about, such as religious reasons, staying home to take care of children/sick relative/friend/pet, or a lost pet. While all these may sound reasonable, to some employers, nothing short of a disabilitating illness or injury is considered acceptable for absence. Other things to be careful of, are information about yourself that they might see as a potential safety or legal issue (that last I think was already mentioned, but bears repeating). Say, sporting a long beard or hair when applying to work in a machine shop where it might get caught in a machine or be a fire hazard in somewhere that has open flames such as a kitchen.
In short, be careful of the information that you volunteer without being directly asked about it.
The only place I even might be thinking that asking the lgbt question could be appropriate, would be in a job where the majority of the clientele IS lgbtq, and in the interview finding out if there was a particular group of clientele that the applicant might be particularly knowledgeable about the customer's problems. Though the applicant would probably volunteer that information in such an environment, anyway, to enhance their own chances of employment; so it might not matter if asked or not.
Plan for questions, and plan your answers ahead of time. This way you're never put 'on the spot' with trying to invent some witty or terrific response.
