Here are some general tips and tricks that will help you to keep the size and performance of your Revit files under control:

• Break up a large model into multiple files and link the files together if you are experiencing performance issues. This will work best if you can work on one file while the other links are unloaded most of the time.
• Purge unused objects. (Note: Purged objects cannot be recovered, so please make a backup of your project before purging.)
• Remove any unused design options. Even though options may not be active or visible, when changes are made within the main model, all design options have to be updated.
• Remove unwanted raster images or renderings, as they can quickly increase file size.
• Do not import a very large raster image and then scale it down to fit the title block. It will retain its original file size.
• Black and white raster images are smaller than color raster images. Save black and white raster images in 1-bit per pixel format instead of JPG. (In Microsoft Paint, this format is called Monochrome Bitmap.)
• Remove unused groups. Delete them from the Project Browser if they exist instead of using the Purge command.
• Create a new, blank drafting view to be used for opening and closing the project. Before saving and closing, open this view and close any other open views. This will prevent unused views from being loaded during startup, freeing up RAM memory and increasing speed.
• Regularly review and fix warnings (click Tools menu > Review Warnings).
• Reduce unwanted data.