My experience and preferences, though I am not "official":
* Put on the wiki
* Any game with a CC License will show you what you can do (usually Attribution, Non-Commercial, Share-Alike). You should contact designers for permissions to translate games without CC Licenses.
* Name the translation page the same as the original, with "(German)" added to the title (see
http://icehousegames.org/wiki/index.php?title=Atom_Smasher_(French) for a sample). I think this is the standard because English is the "official" language of the site and because there's no fully translated full wikis for alternate languages (i.e. it would get weird to have a lot of pages with foreign titles, but no foreign language navigation other than Categories). However, feel free to build a whole "interface" for the German translations, if you wish (I'd start with Main Page, Existing Games, and What Can I Play?, as they are the primary "level 1" navigation pages). In that case, you might want a link to the "German site" on the Main Page (or get an admin to make a link to it in the sidebar or headers/footers).
* Add the Category:German to the translated page, so that it can be found from the Main Page's link link of languages (you'll need to add a link to the German category, once you have a game or two translated and published).
* You might also want to add the title's translation as an H1 at the page top, for the five Germans who can't read English. ;^)
* Inform the designer, or add an Additional Languages section to the original page (see
http://icehousegames.org/wiki/index.php?title=Atom_Smasher#Additional_Languages for a sample).
Those seem to be the Best Practices that we have evolved. Thanks!
David