How do I re-enable the Press and Hold character picker on OS X Lion?

I disabled the character picker by reading this other question, but I want to remove that change and restore the picker.

When I type -g ApplePressAndHoldEnabled -bool true into Terminal, it does not work.

How can I re-enable the Press & Hold character picker after disabling it?

The command to enable the Press & Hold character picker is as follows:

defaults write -g ApplePressAndHoldEnabled -bool true

^{Note the addition of defaults write which was missing from your command.}

If it does not work in certain apps after performing this, restart/reload those apps (e.g. killall -HUP Finder). Alternatively, log out of your user or just reboot your computer.

As grgarside mentioned

defaults write -g ApplePressAndHoldEnabled -bool true

will enable Press & Hold. But just in case anyone comes across this, this additional command will enable the Press & Hold functionality to work in Terminal as well which it does not do by default.

defaults write com.apple.terminal ApplePressAndHoldEnabled -bool true