2) rub your palms rapidly together for about a minute, or until they start to tingle and buzz. (This process opens the hand chakras and allows energy flow. Then hold your hands together, palms facing one another, about three inches apart until you feel energy building up between them.
After the ball is made and sufficiently resized to whatever size the group wishes, you start playing catch. Here's the fun part. You're taking this ball of energy and CHANGING it. The person you throw it TO has to tell you how. (To change a ball of energy, just vizualize it. See it in your hands as it is now, and will it with your mind to how you want it to be. Feel it change and it will change.)
The easiest things to start with are size or weight. Ie, you take a tennis-ball sized thing and make it like a soccer ball, then you throw it. Or you can take the same-sized ball--say a soccer ball, and you can make it balloon weight, or make it heavy like a medicine ball. They catch it, tell you what size it is, visualize resizing it, and throw it on. Many times, they're goin to *subconsciously* catch it correctly for its size before they realize what size it is.
An alternate version for the fully doubtful is to have the former write down what it feels like, throw it, have the catcher write down what it feels like, then compare notes. This prevents "influencing" opinion by the other person. As a training exercize you might want to have all members write down how they sense it, and compare notes.
Once you have size OR weight down well among the group, go for both. The next advanced step after that is COLOR. You set a size, usually soccer ball size for ease of seeing, and you make it a color, or a pattern. Hot pink, blue and silver swirls, green with ugly sylized flowers on it, doesn't matter. But you catch the ball, tell the group what color it is, then make it your color then throw it on. (again, for "proof" have the whole group write it down.) The most advanced form, of course, is size, color, and weight. Changing shape is not recommended, in general, as it's harder to catch, say, a pyramid. ^_^
However, having mentioned shape, shape was part of the FUNNIEST game of catch i ever played, and the one that probably made me believe more than anything else. I was at a "Magic 101" workshop last year, and we were playing catch as a warmup. It went as normal--we'd played before, so everyone was getting pretty good at the game. Then suddenly, the "TA" of the workshop, as it were, decided to be truly evil. (She's really good at truly evil *grins* ). She threw the ball at one of the guys in the group, and instead of catching it like a soccer ball like everyone else, he made this odd grabbing motion like you'd make to catch a tube sock thrown at you, snatching it out of thin air. He blinked, having no idea why he'd just caught a BALL like that, then looked. We all looked. And dangling from his hand was a "bunny-ball." Not an energy rabbit. a BUNNY-BALL. Soccer-ball shaped, sized. But it had fur. A tail. and Ears. And it was dangling oddly from his fist, by its ears. This ended the game, of course, since after we realized what happened no one could BREATHE from laughing os hard for a good five minutes...