to say that you would like to see or speak to someone

A young man was here asking for you this morning. 今天上午有个年轻人来这儿找你。

If you say you couldn't ask for someone or something better, you mean that that person or thing is the best of their type.

She's great to work for - I really couldn't ask for a better boss. 为她工作特开心——我真觉得再也找不到比她更好的老板了。