know sth inside out
对……了如指掌
- He knows the system inside out.
他对该体系了如指掌。
be in touch
了解最新情况
- He's not really in touch with what young people are interested in.
他并不真正了解年轻人现在对什么感兴趣。
know your stuff（英式英语以前也用 know your onions）
精通业务，懂行
- Once you know your stuff, you'll look like an expert, too.
一旦你精通了自己的业务，你就会像个专家。
have a familiar ring (to it)
耳熟
- Her name had a familiar ring to it.
她的名字听起来耳熟。 - I didn't know who was speaking, but his voice had a familiar ring.
我不知道谁在说话，但是他的声音听上去耳熟。
ring a bell
听起来耳熟
- His name rings a bell but I can't think where we met.
他的名字听着很熟，但我想不起我们在哪里见过。 - The description of one of the lads is definitely familiar. It rings a bell.
对其中一个小伙子的描述确实似曾熟悉。听起来挺耳熟。
