Steps to log-off in windows 8:
Step 1: To logoff hit the
windows logo button on the keyboard or click on
windows start menu button.
Step 2: On performing any one of the action, you will be led to
Metro UI window. On the Metro UI you will see User name with a icon, as shown in below image.

Step 3: Click on the
user name or on the
icon a small dropdown menu will appear on your screen, as shown in below image.

In this dropdown menu click on
logoff button, these are the steps to be followed to logoff in windows 8.
Steps to Switch users in windows 8:
Step 1: To switch users just hit
windows logo button + L button on youre your keyboard. On performing this action, current user will be locked.
Step 2: On performing this action current user will be locked but not logged off. Now scroll and click on the left side facing arrow beside current user name.
Step 3: After performing this action you will be led to a window. This window shows you all the available users. Click on any of the users along with their password if they have any and hit enter.
These are the steps to change/ switch user in windows 8.
source:Windows tips and tricks/technoon