Here's a mnemonic to keep them straight in your head
Que (without accent) is translated as "that"
Qué (with accent) is translated as "what"
Here's my mnemonic:
When someone speaks with a heavy accent, they can be hard to understand - and you might even respond with "What?"
Therefore, the Qué with an accent is "What" - because a thick accent will make you say - "What?"