I have never done a lesson with lesbian, gay, or bisexual content. What do I need to think about?

You need to prepare as you would, in doing any lesson. It would be useful to make sure you have grasped elementary knowledge of the subjects, so check out the glossary and be aware of the legal standing of LGB people. Know that by including LGB people and issues in your lesson you are complying with the Public Duty of the Equality Act. See how here. Have some prepared statements in your mind to deal with prejudice and ignorance see