Room treaments

I am beginning to treat my listening room now.
Question what is the preferred room treatments for more seasoned audiophiles with dedicated rooms. It seems there are quite a few members that have great wisdom in this area and we newbies would welcome feedback.
Absorption or difraction/ diffusion or combination of all

Here is what I am thinking to begin.
Absorption at first reflection points (using 2 x4 acoustic panels on side walls)
Thick carpet between speakers and listening position
Ceiling Absorption( same 2 x4 acoustic panels)
Back wall combination of difraction/Absorption
Front wall Absorption.
Corners floor to ceiling bass traps.