为你回答如下：

(1) 如果句子后面动词为及物动词则不需要倒装。例如：

in the room he found his pen.

=He found his pen in the room

=Found in the room was his pen by him.

如果一定需要倒装，可以按照下面倒装(过去分词+介词短语+助动词be+主语+其它）

【结构为：过去分词/过去分词短语+be+主语】 

Seen on the right were the foremost lines of the students by Mr.Fleming 

=On the right Mr.Fleming saw the foremost lines of the students.

=Mr.Fleming saw the foremost lines of the students on the right.

(2) 如果后面动词为不及物动词，则需要到状语。例如：

倒装结构：（介词短语+be动词+主语）结构

By the window sat a young man with a magazine in his hand.

=A young man with magazine in his hand sat by the window.

In front of the house sat an old man.

Among these people was his friend Jim.

=His friend Jim was among these people.

他的朋友吉姆就在这些人当中。

Around the lake are some tall trees.

=Some tall trees are around the lake

湖的四周有些高树。

Among them was my friend Jim.

=My friend Jim was among them.

他们当中就有我的朋友吉姆

倒装结构：（介词短语+动词+主语）结构

On the ground lay a goat.

Outside the room sits a little dog.

一只小狗坐在房间外

A statue, the star of hope lies on the riverside . （自然语序）

On the riverside lies a statue, the star of hope. （倒装语序）

一座碉楼座落在山顶上。

A watchtower stands on top of the hill. （自然语序）

On top of the hill stands a watchtower.（倒装语序）

状语或表语位于句首时的倒装

为了保持句子平衡或使上下文衔接紧密，有时可将状语或表语置于句首，句中主语和谓语完全倒装：

(1)谓语是系动词be时，表语为形容词提前时，整个句子需要倒装.

【结构为：形容词/形容词短语+系动词be+主语】

Present at the meeting were Professor White and many other guests.

Happy is he who devoted himself to the cause of communism.

(2)谓语是助动词be时，表语为现在分词提前时，整个句子需要倒装.

【结构为：现在分词/现在分词短语+助动词be+主语】

Growing along the road are some wild flowers.

Lying on the floor was a boy.=A boy was lying on the floor.

Standing beside the desk was a teacher

Walking at the head of the line was our teacher.

(3)谓语是助动词be时，表语为过去分词提前时，整个句子需要倒装.

【结构为：过去分词/过去分词短语+系动词be+主语】

Seated on the ground are a group of young people.

A group of young people are seated on the ground

(4)谓语是系动词be时，表语为代词such提前时，整个句子需要倒装.

【结构为：代词/such短语+系动词be+主语】

Such are the facts. 

=The facts are such.

Such a great scientist is Yuan Longping.

=Yuan Longping is such a great scientist.

Such was the story he told me.

Such was Albert Einstein,a single man of great achievements.

(5)谓语是系动词be时，表语为介词短语提前时，整个句子需要倒装.

【结构为：介词词短语+系动词be+主语】

Among the goods are Christmas trees, flowers, candles and toys.

Christmas trees, flowers , candles and toys are among the goods.

Among these people was his friend Jim.

他的朋友吉姆就在这些人当中。

Around the lake are some tall trees.

湖的四周有些高树。

Among them was my friend Jim.

他们当中就有我的朋友吉姆

On every piece of paper was a picture of a horse.

(6)地点状语提前时，为了保持句子平衡且谓语动词为be, stand, sit,lie,come等动词时候，整个句子需要倒装.

【结构为：介词词短语+谓语动词+主语】

By the window sat a young man with a magazine in his hand.

=A young man with magazine in his hand sat by the window.

窗户边坐着一个年轻人，手里拿着一本杂志。

From a speaker on the wall comes the doctor’s voice.

On the ground lay a goat.

Outside the room sits a little dog.

一只小狗坐在房间外

我们学校江边有一个“希望之星”的雕塑。

A statue, the star of hope lies on the riverside . （自然语序）

On the riverside lies a statue, the star of hope. （倒装语序）

一座碉楼座落在山顶上。

A watchtower stands on top of the hill. （自然语序）

On top of the hill stands a watchtower.（倒装语序）

Under the tree sits a beautiful girl, reading.

South of the city lies a paper-making plant.

Eventually they arrived at a cave, in front of which stood a tree.

At the foot of the hill lies a beautiful lake.
The soldiers ran to the building, on the top of which flew a flag.
East of the lake lie two towns.
Under the tree was lying a wounded soldier.

A beautiful lake lies at the foot of the hill

At the foot of the hill lies a beautiful lake.

In front of the house stopped a police car.

Nearby were two canoes in which they had come to the island

Under the tree sat a boy

【特别注意】

在表语置于句首的这类倒装结构中，要注意其中的谓语应与其后的主语保持一致，而不是与位于句首的表语保持一致。比较：

In the box was a cat. 箱子里是一只猫。

In the box were some cats. 箱子里是一些猫。