before you：在你面前。
例句：
Please unplug the TV before you go to bed.临睡前请拔下电视机的插头。
Could we have a word before you go to the meeting?你去开会之前，咱们能私下说句话吗？
Get out of those wet clothes before you catch cold.把湿衣服脱掉，不然要伤风的。
Go over your work carefully before you hand it in.交作业前要仔细检查一下。
Try on the shoes before you buy them.买鞋要先穿上试试再买。
Cut up the carrot before you put them into the pot.把胡萝卜切碎後再放进锅内。
Examine the account well before you pay it.在付款以前仔细核对一下帐目。