I just do a quick outline in Obsidian Portal, with links to any pertinent pages. I find that my players often go "off script", so over-prep is typically wasted.
Example:
Rhythmic Evergreen (gate connects to Blitzheim)
Trees have clockwork interiors and circuit-like metal tracing on the outside. They are logged for both wood and metal, but are uniquely useful for the creation of prosthetic limbs.
Loggerhead – Town
Town made from clock wood, surrounded by a pallisade of interlocking gears on stakes, driven by a windmill.
Town by Lindsey Bushby (short and stocky bugbear with an eyepatch)
Guard lead by Wyatt Linen (muscular human with heavy scarring)
Hermits
Tess Janke (Short Wood Elf Huntress/Chef who smells like a smokehouse)
Augustyn (Halfling witch whose eyes have turned white from moonberry addiction)
Alden Pedro (Short Half orc who wears nothing but a loincloth and is training as a pugilist)
Heliotrope
Drakonis Syndicate town
Town built of giant white spore mushrooms
Reached via a split amethyst
Ruled by young amethyst dragon Niasavath
Rhythmic Evergreen NPCs
Blood cult is lead by Kesk, a lizardfolk druid (MM 309) – CR 2
Lizardfolk CR 1/2
Uses scarlet scorpion-like insect to transform the townsfolk into zombies
Scarlet Zombies CR 1/4 (MM 434 with Infectious Bite)
----------------------------------
The best GM I know doesn't really use notes (except for custom creations, like monsters). He just scribbles a map and works from that. His method seems like madness to me, but it works for him.