There are several lines that should be removed from a map before releasing it to the public. Most of these lines are refreshed by the server, so they just take up space in the file, while others can cause console error spam and possibly crash the server. To do this, you will need to open your .mis file with a text editor.
First up, I shall go through the more common lines that need to be removed:
Most of those will be found in StaticShape, Item and Turret, but can be found elsewhere so keep an eye out for them.
Once you've removed those lines, then you need to remove anything that is unused. These tend to be the following:
If you need an idea of what a clean mis file is supposed to look like, check out one of the default maps in missions.unf.