Avoid 『we』, because it is often unclear who 『we』 refers to. You and your marker? You and a co-author? The whole world???
It is also very bad style to refer to yourself as 『we』—writers sometimes do it when they have problems with their essay and they want to 『distance; themselves from it, saying in effect, 『Do not blame me for this result』.
Avoid 『we must teach like this』 or 『we should concluded that…』. If you do this, you are making two mistakes. First, you are telling your marker what to think and do (not a good idea) and second, you are limiting your own position. You are saying 『things are defined and clear cut』, whereas they are often NOT!
You
Avoid 『you』. It is too personal and conversational. That the 『expert talking to learner』 style used in textbooks and handbooks is NOT appropriate in formal writing, since you are still a learner.
I
You can use 『I』 at several points, but making certain the sentence refers to something you are, as a student and as the author of the assignment, responsible for. Thus you could put 『I shall divide the argument into two main sections』 (you could also write 『the argument is divided into two main sections』). On the other hand, you do not want to write, 『I have argued elsewhere that adults learn grammar faster than children』, as this makes you sound like a world expert with 30 books published!
Try and avoid 『I think X is a good idea』. We want you to argue the case WHY X is or is not appropriate, rather than simply assert(=state) that you think it is. This is one of the big differences between conversation and university assignments. In an assignment, you have to make sure you give the evidence for opinions and you need to use impersonal verbs like 『seem』.
Thus you would write, 『Smith would seem to be wrong in arguing that…』 or 『This seems incorrect』, rather than 『I think Smith is wrong』.
有时候，主语I,We后面常常紧跟动词，这样的情况下，可以用[形式主语it] 来改写句子，例如I think，I believe，I feel，I argue，I agree 等等。都可以这样换：I argue that prices should be higher.可以改写成It is argued that prices should be higher.这样在本质上，[形式主语it]都是对原来句子的一种改写，这在学术论文里是非常常见的，常用的大概是以下：It should be argued that…，It has been suggested that…..，It can be seen that….，It appears that…..，It was said that….，It is generally agreed that….，It was found that….，It could be concluded that…，It is doubtful that，It tends to be…，It seems that….，It is widely accepted that…。
2. 更换主语，也就是多使用被动语态。
由于是中文的思维惯性，在我们写论文的时候，都是顺著惯性大量使用有灵主语（I，We，you，me）等。在我们的汉语里，主语一般都是有灵的，再说的俗一点就是有生命的，它们往往都是句子中陈述的对象，指明说的是「什么人「或是」什么事「。中文的习惯是以人做主语，动作的发出者一般是人。而英文，有一种实践，是以物、或者抽象名词做主语。一般认为这是学术、正式写作的惯例，但也有一个很有力的趋势是要求写作更为人性化，有人味。一般认为这是学术、正式写作的惯例，但也有一个很有力的趋势是要求写作更为人性化，有人味。例如，描述一个实验。中文的习惯，是我们怎么怎么设计，（我们）采用了什么什么方法，（我们）得到了什么什么结果。这里就有很多人（人称代词）。（PS，发表文章里，少有单一作者，所以 We 出现得远比 I 多，显得特别团队，特别有气势。I 就感觉上是一个人在胡搞瞎搞，特别弱。）按照去掉人的英文实践，就是：实验的设计是什么什么样的。按照去掉人的英文实践，就是：实验的设计是什么什么样的。这里的主语，或者是具体的物体，或者是抽象的行为和概念。人，都是隐藏在后面的。显得就客观多了。在大家写作的时候，应该有意识的扭转惯性，主动更换主语。
