For uncooked, I drain off the water, mash them, then add back packing water to get the proper consistency, then use salt and/or sugar to balance the flavor if needed.
For cooked, here is the list of things I always put in the sauce, along with very approximate amounts:
1-28oz can of tomato sauce.
2-4 tsp sugar (I use un-processed brown sugar).
1-2 tsp salt
1/2 tsp coarse black pepper.
2 cloves, crushed.
10 shredded leaves of Basil, fresh or about 1 tbsp of dried.
Dash of dried Oregano.
I also sometimes use paprika, red pepper flakes, and various other herbs and spices, although I never use onion or garlic in the sauce (unless it is marinara).