As instantaneously and painlessly as possible and preferably on my own terms.
I'm not sure of the best way of achieving this practically. Shooting myself in the head seems like it would work, but guns aren't readily available in the UK and I've heard of people surviving being shot in the head before, which is something I'd definitely want to avoid.
The method that has been floating around in my head most for the past couple of months is jumping head first off of the tallest easily accessible building I can think of (specifically a multi-storey car park which I think has an accessible roof or at least some openings on the lower floors I could climb out through). I figure that would cause enough damage to kill me on impact, but again, the risk of surviving with just a broken neck and severe brain damage, or maybe just a bunch of broken bones if I panic and fail to land on my head, isn't appealing. Jumping at night, with as few bystanders around as possible, might delay medical attention long enough for me to bleed out on the pavement in the event that I survive. Not ideal, but should get the job done and I doubt I'd be conscious even if I was alive at that point, so the result is pretty much the same as far as my experience of it goes.
Hiding in the woods and overdosing is another possible route to death, but it would probably be far from instantaneous and I'd have to somehow find out how to acquire the appropriate drugs and make sure that they're ones that I know will reliably kill me, both aspects of which are outside my realm of knowledge.
Cutting a major blood vessel could work, but it seems like it would be painful and I wouldn't trust myself to get it right.
Other more outlandish ideas include:
- going to a remote area, making a bomb and blowing myself up (impractical, relies on me successfully making a functional bomb and I'd probably end up getting arrested somewhere along the way)
- standing in an open area and holding up a metal rod, in the middle of a storm (unreliable, could survive, could end up standing in a field like an idiot)
- going somewhere extremely cold (I've heard dying of cold feels quite pleasant towards the end, but the hassle of travelling to such a place seems too high)
- swimming out to sea until I die of exposure or drown (not a pleasant way to go and I'd have to travel to the coast)
- becoming violent enough that law enforcement has no choice but to kill me (impractical and I'd rather not harm or inconvenience others on my path to destruction)