what impact tools are needed for subfloor in the basement?
I helped finish a basement 2 years ago with what I thought was the best carpeted floor I have walked on.

Steps


Make sure floor is flat.  It doesn't have to be perfectly flat but pretty close.  Level doesn't matter that much.  A slight pitch to basement drain is fine.  Do not level this pitch.  You should be "leveling" things because of buckling, big cracks, "steps"... 
Lay down 1" rigid foam sheets - the bigger the better.  
Tape the seams.
3/4 inch playwood on top of foam - the bigger the better.  Lay it staggered so there isn't a giant seam.  
Predrill about 8 holes in each piece of plywood (3-2-3).
Predrill 1/4" countersink holes - tapcon screw won't sink on their own.
Drill tapcon screws into concrete floor.  The screws should be about 3 inches long - 1" foam + 3/4" plywook + 1" in the concrete (1/4" for misc gapping) - you can use 2 3/4 if you want too.  I would not go longer than 3 inches though - you do not want to have issues screwing these in.  The depth is just to keep the plywood flat not to keep it from moving.  Laying the sheets right next to each other should do that.


You can lay carpet or engineered hardwood on this.  Provides a thermal break, a way for water to escape, and is virtually noise free.  Some people will say you don need the tapcon screws.  You do.  I have personally seen a short period of moisture make 3/4" plywood curl up in a basement after it has been down for years.