My daughter is on a gymnastics kick right now and seems to spend about half her waking hours standing on her head. I've watched her come in and out of this pose every which way, including flipping all the way over, something that would alarm most adults but she seems to enjoy. In trying to keep her alignment safe, I've come up with a few ideas about headstand preparation.
If headstands make you nervous or you don't feel ready to come all the way up, don't push it. It's fine to stay in the prep position illustrated here. Work on getting your hips over your shoulders as this is the alignment that will allow you to balance if you choose to come up eventually.
Many people learn to do headstand at the wall, and that's fine, but you should still try to come up with as much control as possible. Don't just fling yourself at the wall as that is a good way to tweak your neck. Even when you are using the wall, don't forget to press strongly into your arms.`
Some teachers advise that you only come up with both legs simultaneously, either with the knees bent or the legs straight. I think it's find to come up one leg at a time if you can do so with control, avoiding the above mentioned flinging.