I didn't feel much at all until I was in a very bad way. My ob said that I needed to pay attention to headaches that didn't go away with panadol, stabbing pains below my ribs and visual disturbances... but I didn't have any of those things until my bp was through the roof.
This time I had high bp and kidney function was borderline dodgy but again I felt OK. Not even any fluid retention.

You don't always have obvious signs, but like Kim said, I did just feel a little weird. So if you feel strange then at least go get your bp and urine checked. It is better to be safe than sorry.