John D. Cook points out that it’s pretty easy to enter accented characters, ç, ü, é, etc., in Emacs by typing【Ctrl+x 8】followed by a punctuation mark and letter. For example, to get ç you type 【Ctrl+x 8 , c】. Cook’s post has a chart of the possible accented characters.
I prefer to use the TeX default input method for entering accented characters but the method that Cook describes works well too. There are more possibilities than those in Cook’s chart. The easiest way to see them is to type 【Ctrl+x 8 Ctrl+h】.