ATC Comms
I am an ATCer and have actually put together a speech on this topic. The 7110.65 is the FAA Order that governs air traffic (FARs are not needed since we are internal employees, for now anyway). In addition to that, each ATC facility has a local SOP approved by the Air Traffic Manager. Therefore, each facility may do things slightly different.
With that being said, make sure you read back anything to do with an altitude, heading or approach. I don't care about hearing the wind check I gave you, but I DO care about the other things.
Also, even though it is a common practice among some pilots not to read back clearances, always read your clearances back (even frequency changes). Don't do the double mic click or just saying your call sign. That does not give the controller the opportunity to listen for a mistake. If a mistake happens, then it creates a lot more work for the controller if you misheard something (or if the controller gave you the wrong clearance).
Make sure you know what the Pilot/Controller glossary says about "Immediately", "Expedite", "Roger" vs "Affirmative". If you are in an emergency situation either use Mayday, Mayday, Mayday or say "Emergency". Pan Pan is still in the book but not in common use anymore.
Finally, realize that most controllers are not pilots. If a controller is not understanding something, tell them in plain language. I worked with a guy that didn't know what steep turns to the left then right actually meant. So if ATC seams confused, spell it out to them (left 360 degree turn followed by an immediate right 360 degree turn).
In the end, the best way is to repeat the clearance back exactly as the controller said it, minus the wind check (or other irrelevant items). The pilots that use their own phraseology for read backs usually are not effective with their read back or take more on the frequency than if the pilot said it verbatim. Eventually you will learn simple ways to abbreviate your read backs while keeping it effective and brief.