Thankfully my iPhone helps me track the dates of my photos and I admit I do have tons of random post it notes and scratch pieces with some random things I don't want to forget all over my craft studio.
But the system I found to be most helpful for being able to catch up quickly is, semi planning and printing the photos I want to include for my weeks.
I'm not inspired by the "planning" piece of crafting. When I plan too much it really takes away from my creative process. And we can't have that happening (wink wink)
I use my Canon Selphie to print my photos straight from my phone. This printer + my iPhone is a LIFE saver when it comes to staying current on PL. Or in my case catching up.
Then if I do multiple weeks at a time. Like shown above. I write on the back of each photo and separate them into the most current week that I am working on.
This seems like a no brainer kind of way. But my desk can get a bit crazy. On top of that I hoard photographs and print doubles and mix them up, mix them up and just plain forget the when's and where's. So this is my best method to the madness.