How to cook good "arepas"?
White pre-cooked corn flour, water, pinch of salt and cooked in the pan is the traditional way of making and cooking arepas.

However, cookery is a living and evolving subject and very much a matter of personal taste. 

I strongly recommend you experiment with the different flours, milk or water or half and half, cooked in the pan and in the oven and decide for yourself which you prefer and which comes closest to the ones you've tried and liked.