How can I reset compiz to the default settings?

GUI Option

For 11.04 and below:

• Log into a recovery console,
• gnome-settings-daemon && gnome-appearance-properties && metacity and press enter.
• When the appearance properties dialogue comes up, change your settings to normal under the effects tab.
• Close this window, and metacity will run (so you can close the terminal)
• Close the terminal to log out from recovery mode, and log back into your desktop.

For all versions:

• Install ccsm (Compiz Config Settings Manager).

  sudo apt-get install compizconfig-settings-manager
  

• Log into the recovery console,
• Launch ccsm from the terminal, (you may also optionally run metacity).
• Create a new profile (if you want to use this method) by going to preferences, and clicking on reset to defaults:

• You can also select the individual plugin causing the problems and reset its values.

Command-Line Option:

Run this command in a terminal (on 11.04 and up):

• gconftool --recursive-unset /apps/compiz-1

On 10.10 and below:

• gconftool --recursive-unset /apps/compiz

Credits to James Gifford for the command.

Roland Taylor's GUI answer broke Unity for me in Ubuntu 12.04. Presumably the "defaults" are the wrong "defaults". Instead, this worked (via the terminal or run prompt):

unity --reset