In a sentence such as "因为我去面试了，所以我刮了胡子", in one case, 了 is after the sentence, while in the other case it's after the verb, even though in both cases, 了 is used to express the past tense.
So how to know where to put 了? Is there any rule to follow?
In my opinion, you can use "了" right after the verb or at the end of the sentence when "了" is used to show the past tense. However, in your case, that's another thing that I want to clarify.
I think, "去面试" should be treated as one phrasal verb, something like the phrasal verb "go fishing", "go shopping" in English.Here "面试" (interview) is a noun which has a verbal meaning, and thus I will treat "去面试“ as one verb, rather than treat “面试” as the object of the verb "去".If you say "我去了北京", it's different because here "北京" is the object of "去“. Treating the two words as one verb, of course you should not insert “了” inside it.
I would say :
I would also say:
Here, “去参加” is treated as one verb and “面试" is its object.
了 usually means you've done something. In most cases it can be put either after the verb or noun in the sentence and makes no difference. But
For example below sentence is equivalent to the sentence in this question.
Paraphrasing from http://www.douban.com/group/topic/11223733/:
The examples in question are excellent demonstration of these rules. 面试 is a (hopefully) long event, and it's preceded by 去, so you put 了 at the end. In comparison, 刮胡子 is a shorter action so you put 了 after the verb 刮.