Ensure all fonts and images are "Packaged" if you are sending the file to someone else, as the IDML does not embed the actual high-res images. To make sure your file converts perfectly, tell me: are you moving from and to? (e.g., v19 to v16) Does the file use complex features like liquid layout or interactive buttons? Are you sending this to a print shop or another that pop up after the conversion.
Keep in mind that this is not an exhaustive list, and compatibility may vary depending on the specific features and elements used in your file.
The simplest way to ensure compatibility is to save your file in a backwards-compatible format. When you save your InDesign file, you can choose to save it in a format that's compatible with an older version. Here's how: