If you get a default font or an error message (such as "can't make font ...") when you request a font:
Check the XLFD name for spelling.
Check the XLFD name for inconsistencies. For instance, you should not specify both the PixelSize and PointSize for scalable typefaces. If you think there might be a conflict, set one of the parameters to an asterisk (*) and try again.
Run xlsfonts to see if the font you requested is available to you.
Run xset q to see if the directory containing the font you requested is in your font search path.
Run xset fp rehash to be sure the X server is using the latest aliases and font paths.