You wait for the scapes to make a full circle and then cut them off.( around June) They are quite tasty and can be used like green onions. They also keep very well in the vegetable crisper in your fridge, and will last for a couple of weeks. Do not pull your garlic yet the bulbs still need to develop. If you are watering your garlic, stop when you harvest the scapes. As for when to harvest your garlic bulbs, I usually wait until the bottom three leaves die off (mid July depends on the year) You want to wait as long as you can so the the bulb fully develops, but before it starts to open. You can test this by exposing the tops of a few bulbs and checking how tight the cloves are to the stem, when they start to pull away, you know it's time. I hope this makes sense.