jugglemonkey wrote:I have employed the old school science trick of putting 2p's in some coca cola and leaving them so they become all new and shiny. Makes them pretty visual on the "flash" scale. I only have one half dollar now and i keep it in a special pocket in my wallet.

Like it.
But doesn't it make your coke taste funny?
Re. MagicDiscoMan... mate, being fair, as long as you're concealing the coin for a purpose, I don't think it matters HOW or WHERE you palm it. It's the effect that counts. I spent yonks trying to learn the classic palm from books, and wondered why it never happened.
Now, I just do it 'where it feels right' in my hand, and it works a treat - and this is, I think (I hope!) how most people learn it.
On the debate of 'which foreign coin/which UK coin', I've never been asked. As I say, if you're doing things on an impromptu basis regularly, it's worthwhile practicing with 10p and 2p (Or, in Taneous' case for instance, your 'common' native coinage).
However - half-dollars seem to be a bit of an 'industry standard' - even though they are not US current wonga either. I think it's their size, their 'tactile' quality, and the fact that the kennedy's have a copper coloured milled edge - making the copper/silver effect possible.
Plus, I find them more of a 'token' than a coin. The routine of manipulating coins could be done with flat washers, as far as the speccy is concerned. It's the effect, I think.
It's also nice to drop them down for inspection afterwards - as the US coinage and more so the Chinese coins have a real magicial quality to people.
Chinese 'holed' coins are also very good, if you can get them in US half size. They make a perfect compliment, and are generally easy to palm. If you're lucky - you can get brass ones with various coloured enamel insets - very attractive.
And as taneous says, it's sometimes an excuse for an elaborate 'plot' or tale, having foreign coins.
Plus - the mystery of an old English Penny (you can pick up a handful of these for about a £1 if you shop around) to people who've never seen one is quite enchanting.
BACK TO PALMING...
I've just thought of something else which may help... the essence of training your hand for a 'natural' looking classic palm takes ages - it doesn't just 'happen'.
You need to be doing it often - walking round Sainsbury's, walking the dog, watching telly. The muscle control needed to be able to just drop a coin into palm is NOT something which us hooomans are born with.
Hints: open your palm flat. Drop a coin onto your palm. Keeping ALL your fingers as straight as you can, bring your TT (your real one

) and the tip of your pinky together. The coin should get gripped. This is only a layman's thing, but this is how I taught my nephew, and within a few months, he was palming coins, balls, keys, all sorts. And he's got a cracking muscle-pass going on.
Cant' think of much more to add than has already been said. One of the best bits of advice was from Nick, who mentioned dry hands... sounds obvious, but as the years have gone on, I've become almost obsessive about having squeaky clean, freshly washed hands when doing coin work. It's a good tip.