Input foreign characters under X11

[Beastie]

Hello everybody.

I've been using FreeBSD for years and never needed to type any non-English text until now. Is there anything like "alt codes for English-language Windows" that allow you to type alt+133 and get an "à" for example?
I'm using FreeBSD 7.2 and trying to get something like this under X11 (plain English is fine for console work). Note that I don't want to change the keyboard layout if possible. I just want to be able to input those alphabetic characters you find in the ASCII extended set.

I've always found all the answers to my questions in the handbook and man pages, but this one is really a PITA and I can't find anything.
I read the I18N/L10N chapters in the handbook and tried to use ISO8859-1, ISO8859-15 and UTF-8 in any of ~/.cshrc ($LC_ALL), ~/.login_conf, ~/.xinitrc, to load iso15 fonts in /etc/rc.conf, and to set the virtual terminal as cons25l1 in /etc/ttys.
I've searched forums and google and the few pages I found didn't help at all.

With UTF-8, all I could get was Chinese, Korean and unknown (box) characters.

To be honest, I don't really know what I'm doing. I don't know what character set to use. I have no idea if I'm doing any of what should be done. I don't even know if what I'm trying to do is possible at all.

Please help before I lose my sanity