Here is some advice we collected for translators:
Only commit translated files in your language's directory. The build process is responsible for adding English files in place of the files you have not committed.
Do not commit translated files into the English tree. Double check your files before committing, to be sure that you are committing to the right place.
Use a system to coordinate with the translators in your language. Currently we have two systems used in parallel, the Translators files and the Revision comments. See the section about revision tracking to learn more about this subject.
While translating, you will find errors in the English manual. If you are sure about an error, that should be corrected, please correct the found errors yourself. If you are not sure, whether you found an error or not, please ask on the phpdoc mailing list.
We have the global entities used all over the manuals in global.ent. If you would like to define entities only used in your language, an ideal place for these is your_language/language-defs.ent. See hu/language-defs.ent for an example.
Do not translate entity names, such as &true; or &return.success;. These are there to be replaced by their relevant text. Translating them only cause errors. Similarly do not translate any tags (eg. <computeroutput>) to your language. The contents of comments (eg. the bottom of every file) are also not to be translated.
Always make sure, that the modifications you made to your language's files, are correct. You may introduce illegal characters. Please always do a make test before committing. Introducing an error in your language's manual can stop the automatic updates online until you correct the error.
If a documentation build process sends an error report to the translation mailing list, examine the problems, and try to fix them before the next build. If you have 'cross reference to paragraphs not supported' errors, you probably have old translated files around. Since paragraphs are generated by the build system for the missing ids not yet in those old files, these errors are inevitable. Either update your translation, or remove the offending files, thus allowing the English originals to take precendence.