Here's a method to remember the order of the reactivity series. You probably have your own ways by now. but just for fun.
It goes like this : Please send cats monkeys and zebras in leathered hired cages, make sure padlock.

Please (potassium)
Send (Sodium)
Cats (calcium)
Monkeys (magnesium
And (aluminum)
Zebras (zinc)
In (iron)
Leathered (lead)
Hired (hydrogen0
Cages, (copper)
Make (mercury)
Sure (silver)
Padlock (platinum)