I find reading, helps to clear my mind of clutter in preparation for concentrating on something that requires my full attention. I also find playing soft music with an easy rhythm and some scents work well too. Of course nothing works better for me than a brisk walk along the sea shore; always clears the head.
I regularly write notes on my calender to prompt my memory; it works too. I also think puzzles and crosswords are a good memory exercise as is reading. Then of course eating foods that are suppose to boost brain function can't do any harm either and a little peace and quiet can do wonders for a tired mind :)