You can now pre-register for a My Nintendo account, which is set to launch some time in March. You can also sign into it using either your Nintendo Network ID, Facebook, Twitter or Google+ account.
If you’re signing up completely from scratch worry not, because you can still link your social media accounts regardless.
Bare in mind, if you forget your password/email while trying to sign back in and you’ve yet to verify your account, you’ll be unable to retrieve it. Be careful. Also, if you delete your account it will delete all data and points associated with it.