bānjiā yǐqián xiě qīngdān, yǐmiǎn wàngjì dōngxi.

Mandarin often leaves out the subject when it is obvious from context. Here, the sentence sounds like a general instruction or reminder:

(You should) write a checklist before moving, so you don't forget things.

You could add 你 if you wanted, but it is not necessary.

以前 means before, and in Chinese it comes after the event it refers to.

So:

• 搬家 = to move house
• 搬家以前 = before moving house

The whole phrase functions as a time expression, and it comes before the main action 写清单.

Yes. 搬家前 and 搬家以前 are both natural.

• 搬家前 = shorter and very common
• 搬家以前 = a little fuller or more explicit

In everyday speech, many people would probably say 搬家前写清单.

In Chinese, when the object is general and the focus is on the action itself, nouns often appear without a number word or classifier.

So 写清单 means:

• write a checklist
• make a checklist

If you say 写一个清单, that is also correct, but it emphasizes one checklist more specifically.

以免 means so as to avoid, in order to prevent, or lest.

It introduces a bad or unwanted result that you want to prevent.

So:

• 写清单，以免忘记东西
• Write a checklist, so you don't forget things

This is a common formal or semi-formal connector in written Chinese.

Because 忘记东西 is a natural way to say forget things or leave things behind, depending on context.

Chinese often leaves the exact nuance to context. Here it means something like:

• forgetting your belongings
• forgetting some items during the move

If you want to be more specific, you could also say:

• 忘记带东西 = forget to bring things
• 把东西忘了 = leave things behind / forget the things

Usually 东西 here means things, stuff, or belongings in a general sense.

It is not necessarily singular. In this sentence, it most naturally means your things in general.

In Mandarin, time expressions usually come before the main verb.

A very common pattern is:

[time] + [verb/action]

So here:

• 搬家以前 = before moving
• 写清单 = write a checklist

Together: Before moving, write a checklist.

This word order is very normal in Chinese.

The comma separates the main action from the purpose/prevention clause.

So the sentence breaks naturally into:

• 搬家以前写清单
• 以免忘记东西

The comma marks a pause, similar to English when you say:

Before moving, write a checklist, so you don't forget things.

Yes. 以前 can also mean in the past or formerly.

For example:

• 我以前住在北京。
• I used to live in Beijing.

But in 搬家以前, it clearly means before, because it follows an event phrase.

They are different kinds of lists:

• 清单 = a checklist or list of items
• 名单 = a list of names

In this sentence, 清单 is correct because it means a list of things to remember for moving, not a list of people.

It can mean both.

In Chinese, 写 literally means write, but in a sentence like this, 写清单 is often best understood in English as make a checklist or write a checklist. Both are good translations.