After you have written your script there are a couple of things you can do to expand on it.

1. Check that you are using steps to allow your NPC to respond differently at different times. Most quest-giving NPCs should have a minimum of three steps: one step for giving the quest, one for while the quest is progressing and one for after the quest is done.
2. Check that all your steps include a click trigger that gives hints to the player as to what he should talk about with the NPC.
3. Include some mention of the overall plot – the plague – in your script.
4. Try to develop links between the quests. Post comments here with suggestions for how others could link to your quest.
5. Flesh out your NPC’s conversation with a few “random” comments. For example, you could have the exit proximity trigger vary between three ways of saying goodbye.
6. We need to help players gather resources, so it is good to have NPCs buy or sell things.