DO supply the printer with ALL of the fonts used to create your project (even the symbol, fraction and dingbat fonts). Try not to use TrueType fonts, and for PostScript fonts, make sure you supply the printer with both the screen and the printer font parts. Remember to include fonts used to create EPS graphics, and fonts that the printer probably already has (i.e. like Helvetica, etc.). There are many different versions of some fonts and a “wrong” version can cause reflow/repagination problems.
DON'T use Bold or Italic in the style menu or hit the Bold or Italic button when you want to bold or italicize text in your page layout program. Use the actual font. For example, in Quark, if you want to create text that is Helvetica Bold, don't select some Helvetica text and then bold it. Instead, select the text and change the font itself (not the style) from Helvetica to Helvetica Bold.
DON'T use TrueType fonts. Period. Always use PostScript or OpenType and Adobe fonts (Macintosh or PC/ Windows) are always a safe bet. TrueType is fine for printing to a laser or inkjet printer, but TrueType fonts can cause severe problems when it comes to commercial printing. Many commercial printers won't even print a project that contains TrueType fonts. Often, they pop.
DON'T use 20 different fonts for a 4-page newsletter. It makes you look like you don't know what you're doing. In desktop publishing, consistency is everything. Use one font for your main body text, another for your main heads, another for photo captions, another for sidebars, etc., but don't mix and match fonts for your main body text or make every headline a different font unless you're trying to create some sort of chaotic effect and it is your intention to confuse the reader. Too many fonts is not only considered to be bad design, but it also slows printing to a crawl.