1. Find the right words for you
You can lead in with a general introduction, such as "I want to ask you about a men's/women's/personal health issue" or "I'm having some problems in the bedroom/with sex."
If you are a man, you might say "I no longer get an erection" or "I don't seem to be able to keep an erection long enough for sex". If you are a woman, you might say "sex is painful" or "I don't experience the same kind of sensations during sex as I once did".
2. Practice at home
Practice in front of the mirror or with your partner or spouse so you get more comfortable describing what happens and saying words that you might not always use.
3. Write down what you want to say
Write down what you are experiencing and your questions. This will help you find the words you need and get the answers you are after. If you find you can't talk about the issue at all, you can give the piece of paper to your doctor.
4. Note what happens and when
Your doctor will probably ask some questions, so keep track of when you experience the problem and what happens exactly. Also, keep track of when things go well, if they do.
5. Get some support
If it helps, ask your spouse or partner to come with you to the appointment. If you prefer, you could ask your spouse or partner if they would ask the question for you, either on the phone or in person.
Most doctors will be supportive and helpful if you raise this issue, but if your doctor doesn't respond well, see another doctor or ask to be referred to a specialist.