There are two options for TF Resets. . .Hard-Reset (Cold Boot) and Data Wipe
For both options, you want to Press an hold the Power and Volume Down Buttons.
The TF will reboot and bring up the ASUS Boot Screen, with the addition of some micro type in the top left corner. (Release the buttons at this time)
IF YOU HAVE THE MOST CURRENT FIRMWARE you will then see a scree with two Icons: On the left is a Box with an Arrow coming out the top, on the Right is the Android Robot.
By default, the Android Robot is selected and the device will automatically "Cold-Boot" within 10 seconds if no other buttons are pressed.
At this screen there are Three Options: 1. Wait for the system to reboot, 2. to confirm the Reboot option without having to wait 10 seconds, 3. to begin DATA WIPE.
The DATA WIPE will clear all data from the Built-in Storage and restore the TF to Factory Default settings.
As far as I have seen (having wiped my device 4 times) it DOES NOT affect the SD Media.
The COLD BOOT is the equivalent of doing a full Power-Down on your Desktop or Laptop Computer.
One final note, be careful which button you press at the selection screen, you don't get much warning if you accidentally choose WIPE DATA. (learned that the hard way :-( )
Hope this helps.