I've tried a number of things, some of them several times: yew poisoning, propranolol overdose, paracetamol overdose, jumping in front of a train, and hanging. They've all failed either due to random chance, being caught in the act, something going wrong, or poor implementation. I was in my early - mid teens when I tried some of them, and I was much too stupid to properly implement certain techniques.
Also, as a kid, I tried jumping out of a window on the 2nd floor, taking small overdoses, and eating batteries. Obviously none of those worked and I'm hesitant to even count them as real attempts, but the intention to die was definitely there.