I've always found that getting them involved asap is the first step to running a junior coaching clinic. Normally a junior's attention span isn't that great so you don't want to spend too long explaining too much.

I've found a good way to start things is by showing them how to swim with the puck and then split them into a couple of teams and let them have a relay race against each other over a short distance.

Once they're bored with this, or have the hang of it, introduce a flick into the relay, or add some extra puck for them to swim around "slalom-like" or out and around a puck and back.

Once they've done that a couple fo times get a games happening. We've actually tried to make it a bit different for the juniors by having sticks a different colour than black and white, such as fluoro yellow and green or red. Seems to hold their attention a bit longer!

Other than that - Good Luck!