Even though I'm a pantser, I write with a calendar beside me, one I made on MS Publisher and print off the year and month/s I need, one month to a page. As I write I fill in the days with what happened in each chapter to help me keep my timeline square.

So for all the plotters, I would recommend doing that. Not an online calendar, but a real one that requires you to fill things in by hand. Why? Because it is right there beside you and you don't have to waste time flitting between tabs, and typing into it - a pen/cil and the paper and you're done.

As for writing retreats...

Here's my notes on the last one I did:

"Note: Writing Retreat! I just got back from a Writi..."

Need to point out, I did end up doing NaNo that year, by the way. It was my second.