i want to travel from Beijing Capital Airport to West Railway Station.

If going during the day, the fare can be CNY120 or around; if at night, you may need to pay CNY140. After landing, you can follow the clears signages which are marked both in Chinese and English, to find the official taxi stands. Line up there and show the note to the driver "你好，我要去北京西站, 谢谢。" You can ask the driver to charge by meter or negotiate the above suggested rate.