Did you register Apple long time before and forgot password? Or do you think one of the apple id is yours, but still you are not able to access it. Don’t worry, you can go here to check your ID and retrieve all your information. You can change or reset the password for your Apple ID account by providing some information.
Enter your ID if you know the ID and need to rest password. The next screen will you give you and option to reset by email (Apple will send the reset link to your registered email. Check here for Apple ID registration process) or you can answer the security questions to reset password from the same screen.
If you forgot your Apple ID, click on Forgot Your Apple ID link (right below Apple ID Enter Box) and answer all those questions in the second screen to retrieve Apple ID and Email.
Check here for Apple ID registration process.