ask for : 解析:　　ask for 的意思是“要求得到”“要求见某人”。ask sb. for sth.的意思是“向某人要某物”“要求某人给某物”。例如:ask sb. for help(向某人求援、求助),ask sb. for advice(向某人征求意见,向某人讨教)。
She asked for time to think all this over. 她要求给她时间把这一切好好想想。
Did you ask (your boss ) for a pay increase? 你请求过(老板)给你加薪吗?
Have you ever asked the police / the teacher / your parents for help? 你有没有向警察/老师/家长求助过?
I am here to ask you for advice (= ask for your advice) on how to learn English well. 对如何学好英语,我来听取您的意见。
注意:　　含有ask for的短语还有ask for a lady’s hand (向某女子求婚),ask for trouble (自找麻烦,自讨苦吃),ask for it (自找麻烦),ask for leave (请假)。