How to enter Greek characters in Emacs

This page indicates that Greek letters can be inserted into Emacs by using M-i. However, Emacs 23.2.1 in a Debian Squeeze variant inserts the "tab" character when M-i is pressed. How can I insert Greek letters such α and β in Emacs?

How do I add Greek letters in gimp?

Select "Use Editor" in the GIMP toolbox to display the text editor and then press "Ctrl," "Shift" and "U" to enable direct Unicode entry. The text editor displays a "u" to represent a Unicode character.

M-x set-input-method RET TeX will allow you to write e.g. \beta to get β, \sum or \Sigma to get Σ etc.

It can be toggled on and off with toggle-input-method, bound to C-\ and C-<.