It might sound easy but bleeding out is actually painful, at least the initial cuts anyways.
First you should choose a place where you wish to cut, the best three places are
1. inner thighs - there should some major artery or something, look it up if you want to know its name.
2. is your neck. You can either sever blood flow from your brain if you cut your left side or air flow into it if you cut from right. Why not both though.
3. is the most often cut wrists. You have to follow the artery though and not cut it across - Go along the street not across.
Whichever you choose you need to cut very deep and prefferably put the wounds in warm or hot water to fight against clotting.
You should also choose a proper tool for the job. Razor blades or scalpels will do the job, but the best choice are straight razors.
One last thing, if you go with hands, cut your dominant hand first. If you cut your other one first you might have issues cutting your dominant with blood gushing from it and the burns, you could also sever some nerves so thats why.
Edit : As for the time, 5-15 minutes until your heart stops. That is in case you sucessfully open the necessecary arteries and they dont have a chance to clot. Considering drinking 3 and more liters of water 24 hours prior to make it smooth.