When you practice Handstand (Adho Mukha Vrksasana), you have to make a real commitment to get your hips and legs up over your head. At first, practice with a wall just behind you so you won't worry about falling over backward. Keeping your weight forward over your hands (toward the wall), push firmly off one foot, swing the other leg and your hips up toward the wall, and immediately scissor the other leg up. It may take much more power than you think! But if you've developed arm strength you can trust, it's time to go for it.
Alternately, you can keep both feet together, bend your knees, and hop up so your hips come above your head. This is a great method for learning the almost weightless feeling of balancing your hips over your hands.