I write notes for myself beforehand too - including my own name, address, phone number, etc. - because when I'm nervous I forget all of that!
I developed a "receptionist persona" back when I had an office job, and somehow I manage to just switch it on, and sound calm, mature, warm, friendly, exchanging all the right pre-rehearsed pleasantries... I'm able to fool people for a minute or so in this fashion, though eventually I will screw up and say something completely wrong, and people will look at me like I'm from Pluto... sigh!
I agree that practice is important. I don't have a lot of reason to use the phone these days, but I'm thinking of just making up reasons to do some kind of business call now and then, to keep my skills up!