The link I gave in the Paella Valenciana description has a typical recipe.
The part that always made the matriarchs (and occasionally the patriarchs) in my family go into dispute with each other involved ñoras and other seasonings. (ñoras are typical of the Alicantinian version of this dish).

Assuming you won't be using the snails (you pick them off Rosemary bushes, starve them for a week and then there's all the business with washing them and tricking them out of their shells) follow Rogelio from egullet's recipe and use the following quantities (for 4 people)

Bomba rice, about 300gms (put this in a cup - you'll need four times this amount in water)
Chicken - 750 gms.
Rabbit - 350 gms.
Grated very ripe tomato - 5 large spoonfuls (an Alicantinian way is to halve it and let it cook along with the meat face down)
Ferraura green beans - 400 gms
Garrofo beans - 80 gms
Saffron - 1/3 gram threads, toasted for about 30 seconds then ground/milled, or one teaspoon powdered colourant (not everyone in Valencia uses or even likes saffron)
Sea Salt (to taste, but no more than 4 level teaspoons on your first run)
pimenton/paprika or smoked paprika (be sparing with this) or freshly ground ñora to taste
small branch of rosemary (lay on top whilst cooking and remove before serving)

The best taste is when it is cooked on an orange wood fire, a little smoked paprika will give a hint of that 'cooked on a bonfire' flavour.

There are no set ratios, so feel free to tweak and adjust to your liking. This is just a guide to get you started.