Your shutter speed depends on what you want to do with the ambient light. Slower shutter speeds will give you more ambient light in your photos, but will not affect the flash exposure at all. The fastest you can have is 1/180s.
Sticking to the numbers earlier, if your subject is at 3m and your ISO is 400, then your aperture will be f8. Now if there is a large room behind your subject that is lit at about 10EV and will not be lit by the flash, then you could set a shutter speed of 1/60s and the room would appear to be normally lit and your subject will be properly lit by the flash. Faster shutter speed would make that room appear to be darker. So you can just green button meter to get an appropriate ambient exposure or underexpose the ambient if you want to.
Using the pop up flash without P-TTL is no different from using a manual hotshoe flash, the concepts are all the same, you just can't change the output of the pop up flash unless you have a K-3.
Last edited by elliott; 12-03-2013 at 10:58 PM.