I’ve tried probably about ten suggestions found all over the web, and this is the only method I’ve found to function universally, across every browser I’ve tested it with.

@font-face {
    font-family: 'NameOfFontFamily';
    src: url('/font/file.eot?') format('eot'),
    url('/font/file.woff') format('woff'),
    url('/font/file.ttf') format('truetype');
}

You can use online font converters to convert an OpenType or TrueType font to *.eot and *.woff as needed. For whatever reason, the “?” appears to be important as well. Not sure about that, I’ll have to look into it further.