I have done multiple things that could be deadly from 12-14, but these weren't done with the ultimate intent of ending my life, like putting an exit bag over my head or suffocating myself and seeing how far I can go before slipping away (hanging russian roulette :P ).
Actual attempts:
1 - 2 years ago when I hung myself, my arms, legs and teeth gums went numb and I got an incredible rush of peace over my head before I passed out. The thrashing became an immediate problem, though. Having your body spaz out and convulse is common during hanging (I had no idea at that time), because of this hanging myself in my room was not an option anymore.
2 - 2 years ago, I reserved a hotel room and wrote a goodbye message on this forum, I brought my nylon rope with me and the note but right when I picked up my bag and went for the door, police officers came barging in and intervened. I was sent to the police station instead in a police car to ''talk it out'', so I wasted my money without setting a foot in the hotel. Moral of the story is: watch what you say on the internet. I still have the nylon rope from that day and I updated the note, but it isn't my time yet. I will know when it is.