This is a part of it, and I hope it could be useful
Try to always start with a magical item, an item of great power. There is always one even it never appears in your campaign!
For example, a special wand that freezes everything for 10 rounds! Isn’t that awesome? Then, who is he who possess that item? Maybe a beggar? No… But wait! Why not? Maybe he once was a beggar, and with that item he became an evil wizard! That’s how the story comes in your mind like a movie film… But what monsters do they follow a beggar who became a powerful wizard? Goblins? No, they are so weak… Orcs? No, they are so stubborn and chaotic… Dark Elves! The dark elves believe in magic! But is this enough to follow a beggar, I think not, and maybe some of them will turn against him! Maybe, not all of them… Maybe one… Yes, the one who calls the heroes to kill the wizard and free their race…
Now go from the end to the start. Start with the final epic battle, where you destroy the evil and you save the world. Design the final room first, where your heroes have the most powerful items to face the most powerful enemy. Write down the skills of your enemy, maybe you will also have to give some artifacts to your heroes. Write them down to create some quests for them. Now you have collect many ideas for 3-4 quests. Design them and you will have more ideas for more quests for your epic travel to the land of the Dark Elves!
Let’s be even more specific. The Evil Wizard will have the wand to freeze you for 10 rounds, but maybe not all of the heroes. Someone should have an artifact to avoid that attack. Maybe it’s a talisman for the wizard. And maybe there is one more item, a wand of time that awakes the heroes with a good roll on the dice. Oh, what quests could give those powerful treasures? Maybe a quest in the High Elves! Why not? Now the story takes an epic perspective. But why they choose to give those powerful treasures to you? Maybe they don’t give them to you… Maybe you steal them! That’s how it works… Now the dark elf who calls you has this great but dangerous idea…
Now draw a path in your map from your starting town to all the important points you should go. Do you have to pass mountains? Rivers? Seas? Does all these makes you want to design more quests? Go for it!
