I used to use my notebook until I discovered that it was far easier to keep track of them on my computer.
I've done it both ways but much prefer the computer. I type much faster than I can write so it's easier to get the ideas down. Back before computers I preferred a typewriter, archaic beasts, though they were. :(
Nope. Not even close!!!
In my head
Computers, that way it's easier to share my work with fellow authors and get their feedback