Engineered/real wood subfloor

[mwkenna]

I am looking to lay engineered/real wood foor down throughout my downstairs. The front part of the living room is floorboards which have raised edges (wavy), the rear extensioin is concrete. I plan to sand down the high spots on the existing floorboards and put a plywood subfloor down throughout the entire downstairs.

The questions I have is, how should I fix the plywood down? Does it need anything between the floorboards and ply to level? How should I fix to the concrete - plugs and screws or some kind of adhesive?

Also, is it still necessary to fit wood-floor underlay on top of the ply subfloor?

Thanks guys - i've fitted loads of laminate over the years but never needed to fit a subfloor.