Each and every coffee shop is different, It's not just the ambience but the staff, flavour of coffee and type of crowd are few solid conditions in order to choose the ideal coffee shop.
Honestly, Living in metropolitan city I come across multiple coffee shops and most of them have a very commercial vibe. But the one I adore is the relaxing homely vibe. With less of crowded seating and people enjoying their coffee and chitchat with less noise.
Idealising a single coffee shop will restrict me from exploring more so, I tend to idealise characteristics which serves my purpose.
Being an architect I always feel happy being in a lit ambience with nice quotes and pictures on the wall of a coffee shop and seating arranged not too closely. I am usually a fan of hand beaten coffee which has a thick creamy texture. On top of that if the staff is polite that surely turns out the best place to be. If I am not with a friend then I tend to take my laptop or a book along inside the coffee shop which is such a relaxing experience and I feel at peace.
Understanding what different coffee shops have to offer is interesting. Like once I went to a coffee shop which had it's own library. How fascinating!
Comfortable chairs and lighting adds up to the must visit list. It's never about the high end coffee shops, rather it's about the comfort and quality of place, people and coffee.
What is your ideal coffee shop characteristics?
I would love to nominate my friend 
