Controller
 

Fig it?s always hard unless you can say ?Speedbird 07 out of 350 for 390. Brits get it.

Now I have a goal... Working on my British accent!!!

Flight levels...
 

+1 with Bob, however...

Might be also heard as 4,000 climbing 26,500, though context carries more weight here.

In the spirit of brevity, I don't even include the name of the controlling facility. They know who they are and don't need me to remind them.

four six Juliet echo, four thousand climbing six thousand.

or final controller for my destination (assuming non-towered):

Four Six Juliet Echo, Four Thousand with the weather and notams. Request RNAV 18. Save at least 2 back and foruth Q & As

Different Controller/Freq - "XXXX Center, RV 904DC FL185" ;) and if specifically ATC assigned, any speed or heading.

Same controller different frequency, i.e. "RV 904DC, change to my frequency 128.2" - if you have coms with standby frequency tuning (flip-flop), just tune and respond on the new assigned frequency. "RV 904DC made the switch" or RV 904DC on 128.2" If you don't have flip-flop coms (not sure they make those anymore) then you should read back the new frequency before switching to confirm.

The whole "with you" thing is an aviation faux pas because of the lack of brevity, even old salty airline captains do this. It's not a big deal until you're in the middle of a NY push and you can barely get a word in. This is where a timely WILCO can work wonders for ATC...unless you're in California those controllers need everything read back with your callsign.

Also there's only 3 controlling agencies...Good Morning, Good Afternoon, and Good Evening

The worst, most incorrect...
 

None is as bad as the dummy that says,
Wait....
Wait...
Any traffic in the pattern please advise.

Well, my wife usually works the radios when we fly and 99.99% of the time she says something like "RV64GH checking in at 8.5". She has worked LAX tower for around 19 years so I kind of follow her lead and so far it has worked out.

I don't think that is a good idea. I often hear people calling the wrong facility on initial call up. Identifying who you think you are talking to on the first call helps to "quickly" identify errors. Without this, when the wrong frequency is dialed in the controller could spend a decent amount of time trying to find the mystery plane that is not on his screen. We follow the same logic when we repeat the clearance instructions or amendments we just received. Yes, it wastes air time, but history has shown that it helps to bring out misunderstandings before they do damage, in the IFR environment anyways. Also, I don't think that I have ever heard ATC identify themselves as "approach" or "center." They always include the facility name and I suspect that is on purpose to avoid miscommunication.

Larry

Include the facility name
 

+1 for including the facility name when calling in.
We can have one controller monitoring multiple frequencies, so it helps them.(Some ATC services have been centralised)

I've been reminded that you want to avoid using the words "to" and "for" as much as possible to avoid confusion. In most contexts they're not needed anyway.