Please..... Before you do anything, research!!
Amitriptyline alone is a horrible death! Wikibooks did have the proper cocktail, but it's been removed for legal reasons.
It listed the amounts and order of taking them. I wish I'd written it down, because I can't remember the doses.
But firstly is the antiemetics! Vital!! The list recommend amitriptyline, diazepam and lorazepam. As well as alcohol. It said to crush the pills and stir with jam or honey, something more palatable. Same for all the pills. Diazepam is a slow acting sleep inducer, but lasts longer than lorazepam. Lorazepam induces sleep quicker, but doesn't last as long, which is why they are both recommend. It also said start taking antiemetics a few days before you plan to suicide, and again 45 mins before the cocktail. I'm almost sure it was diazepam 1st, followed by amitriptyline, then lorazepam. And a good swig of your favourite booze while waiting for it to kick in.
The antiemetics are vital, otherwise you're likely to throw it all up, and death will not be so peaceful. Amitriptyline alone is a horrible death. I know, I saw how my daughter died. Which is why I am going to join her.
Please please read up before you do it and plan carefully.