Many projects don't think about localization until the game is done. Then localization is done as a hack, and it's obvious that it was added on later. Some specific areas of concern:

• Text strings (obviously)
• Audio clips such as music and/or narratives
• Text rendered on textures (e.g. a label on a crate)
• Text rendered in frames in pre-rendered movies
• Fonts/Character sets for different languages
• Etc.

What are some good ways to prepare for these challenges in the initial development stages, so you can make it easier without incurring too much cost up front?