3. Ask questions. Don't make assumptions about anything. If there is something you don't understand or need clarification on, ask questions. It shows your gay loved one that you are making an effort and that you are at least taking an interest in wanting to know more about them. As small as it may seem, it's actually a huge gesture and a bigger step towards a path of acceptance.
4. Don't encourage him/her to change. This is a big thing. I have seen and heard stories of parents and friends trying to encourage or force their gay loved one into a heterosexual lifestyle and in the end, all it does is make them unhappy and drive them further apart. Whether you agree with your loved ones sexuality or not, you have to accept that it's not going to change.
Understand that there is nothing that you can say or do that your loved one has probably not told themselves or done to fight their feelings. By even suggesting it, you are starting something that could cause a lot of damage to their self-esteem and your relationship with them.
5. Love him/her as is. At the end of the day please remember that your loved one is still your son, daughter, sibling or friend and their sexuality shouldn't change the way you feel about them. Do your best to be there and support them as you did before and take pride in the fact they love you enough to share their best gay life with you.
If you would like additional help on this subject, please do not hesitate to involve a helping professional who is trained in LGBT issues. There are various organizations out there that can be of assistance and offer additional information on this subject.