Today's Hanzi is 手(Shǒu) that means "Hand".
The way I remember it is by figuring that the three strokes on the right are fingers, the three strokes on the left are the 3 joints you have on your hand and the vertical one is for the thumb that is opposite to your other fingers.
But really? Only 4 fingers? Just remember Mickey Mouse has only 4 because Disney said it was easier to draw and my mnemonics are all about drawing so why would we want to put 5? :D
Even better, the three left strokes are also pictured in the Mickey's glove, so for 手, just think of Mickey Mouse and you are good :)