Do I login with my email address or my username?
There are two account types - Minecraft accounts and Mojang accounts.
Any Minecraft account created after Fall 2012, or one that has been migrated from the old account format is located on a Mojang account, and logs in with its email address. An older Minecraft account that has not yet been migrated uses the username to login.
You can learn more about the different account types here
I forgot my password
To reset the password for a Minecraft account (you login with your username) visit minecraft.net/password
To reset the password for a Mojang account (you login with your email address) visit account.mojang.com/password
I forgot the email address used for my Mojang account
If you have a Mojang account and have forgotten the email that you log in with, try resetting your password. This will send an email to the address that you have registered, letting you know which address you used.
Alternatively, try other email addresses that you own. If you remember your username, but not your email, visit minecraft.net/retrievename and try different email addresses that you own.
If you still log in with your username, and have forgotten which name to use, you can visit minecraft.net/retrievename to request an email with a list of any usernames registered to that email.
If you cannot get Mojang system emails, visit this article
I need to change the email address used for my Mojang account
To change the email on a Mojang account, visit account.mojang.com/me/settings. You can either have instructions sent to your current address, or if you don't have access to that email, you can have it changed by passing a security challenge.
I remember my email address, but not my username.
If you have a Mojang account, your Minecraft username will be showed in-game and on your Mojang account page.
I've tried the above but I still need help.Please contact customer support through the contact form.