Informal of formal? To me that sounds a little like going to a jobinterview:-)
Dating to me always has been a lot of fun. I never expected more to come from it since you don't control how things will go.
Just date and be yourself, see if there's a click, if you can laugh with that person and if there's more than just the friendly feeling.
I dated quite some guys who are still good friends and I tried out online dating, speeddating, going to bars and dating on holidays. Moslty to enjoy life! And when you think you're dating the person you really want to be with, you'll know from the beginning.
That's where you change your attitude and make sure you're really into that person. Forget the formal or informal way. Just go and have fun:-)