1. Backup apps & data using the Asus appbackup utility in your app drawer. I found it easier to do this in three or four "groups" of apps. Reading, Media, Games, General. Copy these backups to an external storage - microSD, SD or whatever you have. Maybe cloud storage such as Dropbox, or Box.
2. Backup any other files - photos, videos, documents, epubs etc to an external storage as above.
3. Remove the external storage
4. Go to SETTINGS - BACKUP & RESET - FACTORY DATA RESET (Do not allow the automatic reinstalling of apps)
5. Allow the process to finish. When it restarts skip all the account setting up & wifi passwords etc and repeat the process twice more. For some reason it has been reported that doing the wipe three times is more successful, although there is no reason why this should be so.
6. Having reset three times, go through the new install process properly, adding your account/s & wifi details.
7. Restoring Adobe Flash player...
EITHER use the Asus Appbackup app to backup & restore this app (recommended) or, if you have the .apk...
In settings, security, allow the installation of apps from unknown sources.
Copy the Adobe Flash Player .apk file back to your device.
Open the File Manager & tap the Adobe Flash Player .apk file to install it.
Go back to settings, security, & untick (disallow) the installation of apps from unknown sources.
8. From the Play Store update any Asus supplied apps - G+ & Kindle for example, Maps etc, etc
9. Finally, restore your photos, docs etc & reinstall your apps from the backups, one group at a time & cold boot between each group that you restore. (Unless you are resetting because of system instability. In which case, read the next section, first.)
10. Now do a Cold Boot (aka Hard Reset). This cleans system caches, but does not delete any user data.
Unplug the power cord and shut the unit off. Press and hold the VOL DOWN and then POWER button at the same time for at least 10-12 seconds until after the start-up screen appears and is joined by some small print at the top left of the screen then let them both go. If the TF booted the way it always does, you have not accomplished the task, try again until you have seen the 2 icons, (if you have Jelly Bean there will be 4 icons, the left most being RCK, which is correct), in the screen.