To elaborate on what Blaki said, also be sure to add in a "readme" file to your compressed (zipped) folder.
To zip a folder, create new folder on your desktop, right-click, and select "send to... zip folder."
Also, when you export your map, it is very common that any and all particles/weathers/objects will be duplicated in your files, causing your game to have an error on startup. MAKE SURE YOU GO IN AND DELETE THESE. They will have the endings of _0, _1, _2, etc. If you even have one of these, your game will twitch out.
Good luck and Happy Sharing!