Paradox's response if a good one. Just remember, ALL junipers will prefer to live in drier soil than in moist soil. That said, even desert juniper species need water -- especially when they are in a pot.
Here's a good way to determine when to water. Keep a stub of a chopstick or a wooden pencil jammed into the soil. remove the stick daily and feel the dirty end. If there is ANY moisture on the stick, do NOT water. If it feels dry, water. It is best to water from the top with a watering can. Water until it runs out throught the drainage hole in the pot's bottom. Let it drain. Water again.
Then start checking the stick dail again. For best results keep the stick jammed into the soil; poking it into the soil gives poor results.