Write down the address before you forget it.

把地址记下来，免得忘了。

《牛津词典》

You'd better write down her phone number before you forget it.

你最好把她的电话号码记下来，免得忘了。

youdao

You'd better do it now before you forget it.

你最好现在做，以免忘记。

youdao

Keep a pad of paper and pen by your bed, that way, when you wake up in the middle of the night with a burning question, you can write it down before you forget.

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