To answer that question, here are some useful links for you:
NASA - Astronaut Selection.
ESA - Astronaut Info.
ESA - Astronaut Selection.
As a minimum, you're looking at:
. Good physical health.
. A Masters Degree in a technical field.
. At least 3 years experience working in a technical field.
Piloting skills are desirable, but not required.
NASA will fly people to the ISS until 2020, just as they have been doing for the last 10 years.
The only thing that is different now is the vehicle they will use to get there.
Instead of launching on Shuttle & Orion, they will now launch on Soyuz and commercially developed crew transportation vehicles, such as Dragon, Cygnus, and Dream Chaser.