Here is a handy list of translation and localization-related resources for user experience professionals. Following these will help you design an easily translatable user experience. Most of the references here are for web pages or software. Fundamentally, remember your designs will be consumed globally, and never divorce the design process from the development or deployment effort that goes into bringing your designs to life in code.
Ask yourself today: Do you know how the text you are using in your designs are delivered to the customer, even in English?
Key areas that UX designers always seen to fall foul of, in my space anyway, are:
Terminology that is impossible to translate (jargon, multiple modifiers, gerunds) or is used inconsistently
Poorly written, verbose text (really, just write well in English, no special considerations)
String construction (concatenation of parts assembled dynamically)
Composite widget positioning (my favourite)
Hard-coded fonts, small font sizes, or character formatting or casing that doesn't work globally
Format that is not separate from content
Restricted real estate not allowing for text expansion in translation
Forcing formatting with breaks, and hard-coding alphabetical sorting
Graphics that do not work in Bi-Di languages (because they indicate directionality and can't flip) or contain embedded text. The problems of culturally offensive icons are well known by now in the enterprise applications space, though there are some dangers, such as the use of flags to indicate language, for example.
Resources
Internationalization Techniques: Authoring HTML & CSS
Global By Design
Insert Title Here : Variables in Interface Language
Prose: Internationalisation
Doc and help considerations I can deal with later.