1. Write your quest out - a rough draft if you will. On paper, on PC, whatever. Have a solid idea of what the main plot of the quest is.
2. Write a story! It doesn't have to be perfect or too long, but taking the time to write a story will really help you in the next part. We need to know where things are happening, who is involved, how did we get here... And why?
3. Write your core dialog with the character you created. Take instances from the story you wrote, and make a game-style dialog out of it. Use a word processor or notepad. Make sure you clearly mark whose lines are whose. Feel free to add some director's notes, also marked clearly, indicating any action or background that occurs in the talking scenes.
4. Get that stuff done.
5. Come back, and we will help you make your mod happen! You will need to read some tutorials, but we wil also help you find them and get things moving quickly. If you take the time to do the steps provided, this is a do-able starter mod that will teach you a lot, as well as making something cool you can share and be proud of!
We also are much more willing to help when you can show us that you are serious and have put in some work. I for one will help you with scripting stuff, when the time comes