I am starting a detergents factory. And I am confussed, should I start advertising before selling, or do I present my products to the supermarkets and wait for awhile and then advertise?

I would advertise first. Get the name out there. Product recognition is key. Then when your customer sees your product in the store, they will say to themselves, "oh, here is that detergent I've been hearing about. I think I'll try it".

Good luck.