I've only attempted hanging twice before. Well the basic rules would be to have a decent support, something that won't break under your weight.
Other thing is having a "rope" that is comfortable for you, too thin and it might hurt, too thick and it might not work properly.
Also there are two types of hanging, with a drop or suspension.
With a drop the death is instant as you break your spine in the fall - there is some chart on the internet that measures how much of a drop length you should have depending on your weight to make the death instant. In the worst case if the fall is not big enough you could merely inflict permament damage on yourself and not die.
The other type is hanging without drop - suspension, the cause of death there is asphyxia, in other words lack of oxygen supplying the brain. This one takes longer, up to 15 minutes until your brain dies. You should lose consciousness in about 30 seconds max after you proceed with this. The problem here could be being found, your body will probably spasm even after you blackout, so if somebody finds you in those 15 +- minutes you will have permament brain damage and whatnot else.
Other things to note is to make sure the noose you tie is well done so it doesn't come undone in the middle of the process, could be a big problem.
There is also a door knob hanging method - I've personally done this and it works. If you can't find anything to support yourself like a support frame or something on the ceiling this is a viable method. Its a suspension type where you hang the noose on the door knob and sit down, your body weight will pull you down and that will result in the asphyxia. The important thing there is to make the noose small as possible so the pressure on your neck is greater because you don't have that much space, depending on how tall you are.
EDIT: Also don't worry that you failed with cutting, it is really painful and almost nobody ever succeeds, only about 5 % max of people who attempt it ever die from it, the number is probably even lower.