All writers have their quirks - an attachment to nice stationery seems to be fairly universal, and an awful lot plot by post it note. With me, it's time lines. No, time lines, not time lords. Yes I know there is a new Dr Who on the block, but please try not to let your attention wander.
Time lines - in case you are not keeping up - are exactly what it says on the tin - lines with times - or rather dates, on them. I love them, which is surprising, as I have a terrible memory for dates. I do one for most books, sometimes for lots of events, if the plot is getting complicated, but always for sorting out when characters were born - I like to know where everyone fits age-wise in relation to each other. It's useful too for back story - appropriate names, favourite bands and stuff like that. The prompt for this post was a book I just read - great plot, characters, etc, but something was just a bit off. In the end I realised that the ages of the different generations of the family didn't quite mesh together - not off by much, but just enough to make me unsettled.
Which just shows how useful a time line can be. I like to draw mine diagonally across the page, which is another one of those writer's quirks.
It works for me, better than post it notes - but to each their own.