Time and Money Management Skills!!! I think that these two life skills should be taught to young adults.
The problem with today's generation is that they are so attracted to new technologies and gadgets that when one is released, they go immediately purchase and buy it online. All for the sake of being part of the "cool" one.
While it is no major cause of concern when they have their parents on their side, it will become a huge problem the moment they go out solo in the outside world.
Having a good knowledge on how to manage your money and time is probably the best life skill one should have in today's time as it allows one to survive and live a stress-free life without worrying too much nor expecting too much about anything.
If one can manage his time and money properly, then he's all set for the outside world.