Normally, the mutton is tenderized by using some raw papaya paste. Since I didn't have papaya, I went in for vinegar. You can even use the meat tenderizer you get in shops, though it is not recommended.
Do not dry off the mutton stock after it is cooked. It will all dry off once the dum is done.
Take care while cooking rice. After three minutes of boiling it, check for doneness. If there is a nice bite in it, immediately drain it. It will get cooked while in dum.
I thought the spice was too much when the masala was being layered, however once the biriyani was cooked, there was hardly any! Do increase the green chillies or the red chilli powder if you like your biriyani to be spicy.