Orders
If you know the radical meaning orders you know the kanji meaning orders as well!
Here's an order: study your radicals.
れい
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Your orders are to get a ray (れい) gun.
Imagine an authority figure giving you this order as an official order. Ray guns don't really exist, so you think it's a pretty strange order. Hint: when you see the orders radical, the reading will often be れい. The mnemonic will likely involve orders to get a ray gun of some kind.