Most translations can be made by creating and modifying .po files. However, there are still exceptions to this rule. This page is meant to summarize such situations in GNOME packages.
Default welcome mail
In the src/mail/default/$LANG directory (where $LANG is your two-letter language code), copy and translate the src/mail/default/C/Inbox file
Pangrams shown in font viewers/editors may use the pango_language_get_sample_string() API to get a pangram. Pangrams are stored in the Pango source tree, in /pango/pango-language-sample-table.h. Enter a bug in the pango product of GNOME issue tracker to add/modify the pangram for your language.
Glom's files can contain translations for the various table names, fields, relationships, choices, layout groups, reports, etc. This lets multiple people use the same database UI in different languages. These translations are exported to .po files so translators can use their familiar tools.
These are imported back into the .glom files every now and then.
Feel free to add new .po files, based on the .pot file in the directory.