Guess what the hardest part of modding is?
That's right, it's writing dialog. Writing *good* dialog, that is. Essentially, good dialog means two things to me, two things that what I want to offer the player:
1) NPCs with a distinct personnality - with their own backgrounds and interests.
The first can be achieved in many ways: describing the NPC when the PC first meets him, for example, or giving him a quirk that will define his behavior, or simply having him react differently based on the PC's race or state of dress (or undress). As for the second, it just means having more than one branch to choose from in conversation. The various branches don't necessarily need to lead each time to a different answer from the NPC: what matters is that the player has the choice.
I really liked the way it was done in Planescape Torment, and I've drawn inspiration from it. Especially the [Lie] and [Truth] options - you'll find some in Madness&Magic.
Writing dialog is also very time consuming. Even when writing full tilt, I rarely churn out more than 2000 words a day. Maybe I'm just slow. To make it worse, sometimes in my creative frenzy my brain tend to switch to French. Bad brain. No cookie for you.
Here is an example of dialog in my module.
(Click to enlarge it unless your eyes came equipped with a zoom function.)
In fact it's the very file I'm working on right now. It's part of the main quest of the module: the player is looking for the sphere and that particular NPC happens to possess information about its whereabouts.
You can see I provide a description of the NPC at the start - yet another wizard. Then you've got the main reason why she exists, the question about the sphere. The second option is a placeholder link for another way to get the info about the sphere which is still linked to this NPC - and it's half in French too, because I'm that lazy. The rest is flavor text; it doesn't have any plot relevance but the player can ask her about her appearance and whatnot. The PC's class can change the way she reacts to him, as well as his previous actions.
Keeping the conversation consistent without cluttering it too much is a real challenge. Definitely the hardest part of modding for me. Fortunately it's also what I enjoy the most.
And on that note, I'm getting back to it...