On rare occasion, I like to create my own single missions, usually for quick combat.
I’m careful to first make a new file if one doesn’t already exist and follow Nutcase’s instructions.
Sometimes, not every time, my short and long mission descriptions show up blank when I select that mission from the menu. Yet, I can open FMB, load that mission, open description and see that it was saved.
How do I do it right every time?

Do you ever edit the mission briefings in Notepad? If you do, then hitting the Enter key will cause all text after that to be ignored by the game when you run the mission.

No Zeus-cat, I haven’t edited anything in Notepad. Not sure I would know how to.
I just type in my mission description in the message box, save, and either it takes or it doesn’t.
Would like to hear more about editing in Notepad though. I’m not all that computer literate, but, you know that since playing Il-2 and reading this forum regularly for the past couple of years, I have learned a great deal of the computer skills that I do have!

I'd recommend that you stay away from using Notepad to edit missions for a while. If you're curious to see how the mission files are created "under the hood", so to speak, take a look at a mission you've made yourself (preferably a simple one, to start with). Some of the structure will become apparent fairly quickly. But for mission building, the FMB is graphically oriented and hence easier to grasp, and moreover will give you ample control and should be mastered first.

--Lurch--

I also highly recommend Mission Mate & The Uber Quick Mission Generator.. they both can be found at the bottom of the Nugget's Guide in my sig. Check them out.. you wont be sorry.