Originally Posted by luigimar
There are many factors that affect what coin to use, so this question is not easy to answer.
If you have American coins handy, try classic palming a half dollar and a dollar coin. It doesn't have to stay there forever, just see what is more comfortable for you. Here is an image to give you an idea of where to put the coin (the exact position may vary, depending on the size of your hand):
Now try finger palming the coin...here it is...
now answer this question: Which coin was easier to keep in those 2 palming positions?
Those 2 are basic palming positions and whichever coin was easier to keep might be the best coin for YOU. But with some practice you could try to do coin effects with either of those coin sizes. There are more ways to hide a coin in the hands and most likely throughout time you will keep learning them.
The most common size to use is half dollar but for some effects you might try dollar size. I guess in the end it will be a matter of choice (your choice). If I remember correctly (we had an Eric Jones' lecture almost exactly one year ago here on TMF), Eric uses (silver) half dollars. So I would suggest using those coins which are also more readily available than dollar coins.
But as I said, ultimately it will be your choice...
Also I would suggest getting some basic coin books or books with a coin section within. Lorayne's The Magic Book
is one, Bobo's The New Modern Coin Magic
is another. Henry Hay's Amateur Magician's Handbook
is yet another.
I hope this information helps...