I'm making meatballs in a saucepan. Should I drain the meatballs first or just pour the sauce in the saucepan?

If there's a lot of fat (more than 2 TB) , yes, drain out most of the fat. If not, then just add the sauce.

I brown them in a skillet then transfer them to the sauce with a slotted spoon - draining away most of the fat. If they are big fat ones I will sometimes pop them in the oven between pan and sauce. But yes I would say drain them!!!