To see a sample of one font on a Datadisk terminal, R DDFONT and give it
  the name of the font (e.g. "NGR30").  Say HELP DDFONT for more info.
To print a sample of a particular font on the XGP, say
  R FCOPY;<file name>/INFO/SAMPLE.  Say HELP FCOPY to learn more of its
  capabilities.
To print a sample text on the XGP in a number of different fonts for 
  comparison, say R FSAMPL.
To make a .TFX file for an existing font (needed if and only if you want
  to use this font with the TEX document compiler), say R TFXGEN.
  To edit .TFX files, use TFXPR and TFDRD.  Say READ TFX for more info.
To examine or edit characters in an existing font, use EDFONT, described
  in EDFONT.TVR[UP,DOC].
To edit the characters of a font using E, use FMUNGE, described in
  FMUNGE.REF[UP,DOC] or FNTCHR/CHRFNT, described in FNTCHR.MAI[UP,DOC].
  FMUNGE is probably easier to use; FNTCHR/CHRFNT were designed for use
  with the METAFONT system.
To create a new font use TVFONT, described in TVFONT.BGB[UP,DOC], or
  PIX, described briefly via HELP PIX.
To scale the size of a font use FSCALE, described in FSCALE.DON[UP,DOC].
To combine selected characters from two fonts, use COMBIN (say HELP
   COMBIN for description).
To compile a font, RUN UFC[XGP,SYS].  UFC.REG[UP,DOC] explains what
  compiling a font means, and why it's good for you.
To poke at all sorts of mystic parameters in a font file (not recommended
  unless you know what you're doing!), R FONT.  FONT.BH[UP,DOC] is the
  documentation file for this program.  One warning in particular: Using
  FONT to find out the height or width of a few characters (using the
  "modify chars" option) will cause the file's last-written date to
  change, obsoleting the CFT (compiled font) file for that font.  Make a
  copy of the file and look at that instead.
To learn about the format of font files, see FORMAT.DOC[XGP,SYS].

Some of the above programs append the ".FNT[XGP,SYS]" if you leave it
  out, but all of them (I think) will accept the complete file name if
  you type it all.