Action, 以免 + Undesirable Outcome
以免 means "in order to avoid" or "so as not to," connecting a precautionary action with an undesirable outcome to be prevented. The first clause states what should be done, and 以免 introduces what would happen otherwise. For example, 多穿点衣服,以免感冒 means "wear more clothes so as not to catch a cold."
出门带把伞,以免突然下雨。
Chūmén dài bǎ sǎn, yǐmiǎn tūrán xiàyǔ.
Bring an umbrella when you go out, in case it suddenly rains.
你最好提前预约,以免到了没有位子。
Nǐ zuìhǎo tíqián yùyuē, yǐmiǎn dào le méiyǒu wèizi.
You'd better make a reservation in advance, in case there are no seats when you arrive.
把密码记下来,以免忘记。
Bǎ mìmǎ jì xiàlai, yǐmiǎn wàngjì.
Write down the password, in case you forget it.