I learnt one important lesson whilst gettimg my PPL by having a bit of a disagreement with Sydney departures on-air; between the controller and I, a clearance seemed ambiguous and I thought one thing and they thought another.
After trying to debate my point a couple of times, both sides digging into their position, I thought better of it (I just imagined all those QF pilots sniggering at the verbal ping-pong going on) and decided that politeness was the order of the day.
What did I learn? Firstly, even if you are slightly unsure about what ATC want, ask them; and secondly both halves of the pilot / ATC equation need to remember that we both want an easy and safe flight without any on-frequency verbal lashings. It didn't help them or me to continue the conversation as it was - and when I left their control I thanked the (same) controller profusely for their help, and they were equally polite back. Maybe there is a lesson in here for some of the more hot-headed ATPLs out there...
I have, however, so far avoided upsetting LATCC and thoroughly intend to keep it that way
Paul.