General procedure:
Select object -> Look into the status line:
- 'blahblah... clipped...' -> Object -> Clip -> Release
- 'blahblah... masked...' -> Object -> Mask -> Release
- 'group of ....' -> Object -> Ungroup
- 'clone of ...' -> Edit -> Clone -> Unlink clone
- 'flowed text' -> either: Text -> convert to text (next user must have the font available, and in your drawing, this displaces the text), or Path -> Object to Path (text is no longer editable, but will always look correct).
Repeat until there are no more groups, clones, clipped objects, masked objects, flowed texts etc. in your drawing. This way, you will get maximum compatibility with any and all applications out there that do only support a subset of the SVG standard, or when you cannot know if the user will have the font installed on their computer.