Here are some things to think about when planning a translation project:
Files: Identify all the files you will need to translate, including graphics. Ensure you have all electronic source files for documents; this is especially important for using translation software, and for any images and animations that contain text that needs to be translated or localized.
Versions: Make sure you have the latest or final version of any file you will send to translate. Do not use drafts, or documents that are in review and may still be subject to change.
Selection: Review the source language materials and remove any content that may not be needed in the target language. Whenever possible, adjust the material to simplify the translation process.
Word counts: You will need word counts for all the files to be translated. You can do easily in MS Word files, but if you have a lot of files in different formats, it can become difficult. If you have access to translation software, you'll be able to set up a project, process the files, and generate a report. There are tools that can extract word counts from various types of files (.docx, .xml, .html, etc.), even graphics (.jpg, .bmp, etc.). For graphics, you can also estimate by taking a few minutes to count the number of words in a representative sample of images and calculate an average.
Reference materials: Gather any available reference materials, such as glossaries and style guides, translation memories from previous translation efforts.
Team: Think about the team you'll need to assemble. What language combinations will you need? How many translators, reviewers, SMEs? Will you contract freelancers, or an agency? How will you ensure good communications?
Translation plan: Consider preparing documents that explain the scope of the project, workflow, team members, style, format, and localization issues, expectations, deadlines, etc.