You need to cut the flower heads off so that the plants do not set seed. If they set seed you probably won't get bulbs. The bulbs form under ground. Later, maybe July, the plants will start to turn yellow and die down. When the plants are mostly yellow pull them up and let them dry on the ground or spread out under cover. My husband spreads his out on tables (saw horses with boards or old doors) in the garage. After they dry a few days or longer you can take the upper leaves off & store the bulbs in mesh bags in a cool dryish place. Or use the upper part to make garlic braids. Hope this helps!

Also, if you just can't wait any longer, I've read the leaves taste garlicy, too. You don't want to steal all, or even most, of the leaves, but some is OK. (Cannot convince hubby of this, and he's the chef. LOL)