So you get a computer, and the first thing you do is to create a login account for yourself on it. This account does not have to be given administrator's privileges, and it probably shouldn't have for security reasons. The second thing you should do is to create a second login account on the computer. This account should have administrator privileges. You can give it any name you like as long as it isn't "Administrator" or "Admin," for security reasons.
The third thing you should do is add an external hard drive to the computer and set it up as the Time Machine backup drive. You will never regret doing this.
So why do you really need two accounts?
Sometimes, like what happened to me today, you will log in to your account and discover that not all is right with your login. Files seem to be missing. Stuff in the Dock is gone. Nothing works.
You log into the other account and find that everything is working. That's good. This means that your personal login account is corrupt.
To fix your personal login account, you have to be logged in to the admin account. The steps to follow are simple:
1. Open System Preferences and go to Users and Groups. 2. Delete your personal login account and select the option to move everything to the trash. 3. Close System Preferences. 4. In Finder, go to the Time Machine drive and see what the date is of the most recent backup. Delete the most recent backup if, and only if, it coincides with today's date. You don't want today's backup because it probably has the problem in it. And now you should understand why it is so important to have a Time Machine backup. 5. Open Migration Assistant. 6. Choose to migrate from the Time Machine backup. It will let you know that it will be restoring from the latest backup. 7. Unselect everything except your personal user account. 8. Let Time Machine restore your account. 9. Log back into your account. It should be okay now.
I know that I overlooked a few minor details in the above instructions, but hopefully you'll be able to see what needs to be done at the time you need to do it.