As Metryq says: for PC users, most of the odd characters that you may need are available by holding down the "Alt" key, then inputting a 2,3 or 4 number code on the number keyboard on the right of the main keyboard (Make sure "Num Lock" is on!)
I've this page bookmarked,which gives most of the useful codes:
Alt Codes Reference Sheet
(left-click to enlarge)
Handy for those accented names that JRRT is so fond of!