Haven't done the RT yet but what I'm thinking of doing is plan the route (as per Gonville's suggestion) and write all the R/T down on a piece of paper and hand it to a friend who will be your ATC. That way it doesn't matter if the friend hasn't got a clue what's happening, as long as you follow the script! Oh..one think that I've noticed, it's easy to just look at them and hear what they're saying. Try and keep your eyes focused somewhere else or do it over the phone or something (Yes it's sad but it's closer to real life that a face-to-face chat)!
Hope it helps!
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Quod Me Nutrit
Me Destruit.