I frequently outline each chapter, mostly because I have complicated plots that I can't remember otherwise (I often end up changing things, though.) How much detail really depends on what I'm trying to do with a particular scene, though--for a mostly action scene, I might write something like "Big fight in bar, Bill injured, taken to hospital. Cops called. Laura unnerved. Bartender says man in fedora came in yesterday--what mean for Our Heroes?? We get some of Laura's backstory here--she recalls incident at summer cottage." Or whatever. Usually my chapter outlines end up running 1/2 a page to a page, single spaced, which might cover about 20 pages of manuscript, but that's just a very rough estimate.
With my first completed book (rough draft just finished the 31st of last month) I had a firm background for the first character and I knew his personality. then I set up a series of major events he was going to be involved in. Most he caused, several he was swept up in. Then I decided my starting place and the series of events as they were going to transpire.
It was like this:
Starting Point: Dreadnaught Class Heavy Cruiser, in small cabin.
Events: Imperials Abandon Sector and Turn ship over to formerly figureheaded leader.
Sub-Event: Organize crew
Sub-Event: Arrest Attempt on main character
Event: Pick up Prize ships before Imperials get them
Event: Answer distress call
Event: destroy or run off pirates and save Settlers
Event: Go to Native world with intent to get marines and future base (charter thinks he's saving Settlers from broken ship and finding a safe temporary location)
Event: Bug Menace
Sub-Event: save native bug prisoners
Sub-Event: go down to the planet to secure permission for settlers to land
Sub-Event: former settler escort catches up with the Heavy Cruiser, due to engine troubles
Event: Return to Confederation Space
Co-Event: Mutinous or Piratical former Fleet Mates spotted
Sub-Event: go to deal with them
Co-Event: Imperial Cruiser are seizing Constructor ships that don't belong to the Empire under the auspices they are imperial assets.
Sub-Event: stop those piratical Imperial pirates!
Event: Main Battle with Imperial Medium Cruiser
Its wasn't quite as official looking as all that. However all the Main Events were in my mind. Most of the sub-events were notions of things I wanted to do if I was a good enough writer to fit them into the story. But how I got there was entirely up to me. Which allowed for my sense of fun and adventure to break free without queering the deal with me losing my way from lack of a clear sense of what was going to happen next.
But that's just me and its not yet finished editing yet.
Hope it helps.
The Deposed King