My 14 and 12 yr olds have ZERO common sense. I don't know what to do about it or how to instil it.
I had to fend for myself as a child and moved out of home to live alone at 14, I had a child at 16 so I've always been able to do anything I wanted or needed to with a mixture of logic and common sense and it was those basics that allowed me to learn how to adapt and hone skills.
My children seem to have none which is my fault because I've done everything for them but now I don't know how to give them any.
I'll give you an idea,
I asked them to pop to the local village post office/shop to get a loaf of bread for sandwiches, off they went. An hour later I get a phone call from DS1, they don't have any sandwich bread then only have stuff for toast. I had to explain to him that bread is bread, just get the loaf and bring it home. 
Today, DS1 wants to bake biscuits (by himself) he then comes in a million times, "what does a saucepan look like?" "Can I use corn flour instead of plain?" "How does the oven work.."
This child has been in the kitchen with me from day one, I've always encouraged him to chop, peel, weigh etc. He's also completed a whole food studies term at school but still doesn't have an ounce of ability in the kitchen.
This wouldn't be quite so awful except for years he's decided he wants to be a chef. 
It applies to everything though, how on earth do I get them to have some independence, some ability to just do stuff for themselves?