Here's my approach, based on how 1e advised building a campaign.
The 1e book suggested a campaign outline built on the following:
Campaign goal
Location: where? Will the company range all over or will there be a focal point?
Focus: "What is your game all about?" - War? Politics? Horror etc.
Company: does our Outline offer a reason for the company to gather?
Loremaster characters: who do we want to focus on?
It gave a broad structure and then provided a worked example: "The Darkening of Mirkwood". This worked example then became a full campaign supplement!
My current campaign example:
Campaign goal: to defend the North against a resurgent Angmar, Mount Gram and Mount Gundabad.
Location: where? Rivendell and Bree are our focal points and frequently returned to, with repeated diplomatic trips west to the Blue Mountains/Grey Havens and repeated trips North to scout and defeat the enemy. A tower to be re-established by the Company is another focal point.
Focus: Politics, old enmities, recovering old relics/knowledge to combat the Adversary. "Hope via reclamation".
Company: does our Outline offer a reason for the company to gather? Our High Elf and Ranger knew each other from their time at Rivendell, and Elrond and Cirdan tasked them with recruiting other representatives of the Free Peoples (a Dwarf and an Elf of Lindon) to investigate the growing Shadow from Angmar.
Loremaster characters: Cirdan, Elrond, Gilraen. Gorbag the Great Orc, Maurg the drake and some Ringwraiths. Plus (redacted) the Traitor.
Separately, I also wrote a very simple solo introductory adventure, available here:
https://docs.google.com/document/d/17RS ... -I05U/edit