I would have to say that I think about suicide on a semi-regular basis. Although that may sound pretty awful, at the moment I am the happiest I have ever been in my life, and unlike in years past, I don't want to die. To me suicide is a comforting thought. It's the idea that in the end, I get to control my own destiny.
I was probably at my most suicidal in high school. Living was a chore with few silver linings, and the only thing that held me back was the knowledge of what that selfish act would do to my loving family.
Part of my still occasionally thinking about suicide is advice my psychologist gave me for handling anxiety: instead of stressing yourself out by attempting to avoid thoughts, it's better to embrace them, analyze the symptoms, and then move on with life.
How I would do it at any given time would depend on the resources available to me. Giving a Beretta a blowjob would be my ideal painless out, but I never grew up around guns, so that probably wouldn't be the way in this hypothetical scenario.
I wouldn't try to hang myself since I would probably screw up the knot, and I would want my final movements to be painless - I am trying to end my suffering after all. I also wouldn't slice my wrists, since to die from that you have to cut vertically and then run the wound under water or with salt to prevent the bodies natural blood clotting.
Overdosing probably wouldn't work, since I have already abused a number of drugs to a level that medical professionals have said they are surprised it didn't leave more lasting damage.
My ideal suicide would be in an enclosed garage. I would take a bunch of opioids or benzodiazepines (not to die, just to relax/sleep) and leave my car running while I played something appropriate over my car's stereo and allowed the carbon monoxide to remove me from this mortal plane. Failing a garage, high doses of helium cause death, and I could purchase that over the internet.
That all being said, I have never "attempted" suicide. I've wanted to die, I've comforted myself thinking about how I could make that happen, and in my younger more-emo years I made suicidal gestures, but I have always said when asked by a mental health professional that I've never actually planned to do it. If I ever decide to kill myself, I will, but I have never lied to myself about the subject, and have always stressed that I think about suicide, but don't intend to carry it out.
Suicide is an exceedingly permanent solution that functions in my head as a final out if I am truly done living.