These sentences are in the active voice because they show that the subject acts, or does something: 

The Customer Inquiry Department answers almost four hundred phone calls every day. 

Our new maintenance program saved company $5,000 in the first six months. 

The committee records all suggestions in a log. 

Government must place some constraint' these contracts to prevent price excesses. 

Almost four hundred phone calls are answered by the Customer Inquiry Department every day. 

$5,000 was saved by the company in the f six months of our new maintenance program. 

  All suggestions are recorded by the committee in a log book. 

  Some constraints must be placed on these contracts by government to prevent price excesses. 

1. sounds more vigorous 
2. is more personal 
3. uses fewer words 
4. is easier to follow 
5. is easier to remember 

Cut "I think," "I believe," "I know," "It seems to me that," "In my opinion." 
These expressions weaken sentences. Cut them, and you will make your sentences stronger. 

BEFORE  
We think prices are already too high and know people are hurting. 

AFTER  
Prices are already too high and people are hurting.

BEFORE 
There are alternate ways that must be found by us to solve the problem. 

AFTER  
We must find other ways to solve the problem. 

1. Never use a long word where a short one will do. 

2. If it is possible to cut out a word, always cut it out. 

3. Never use the passive where you can use the active. 

4. Never use a foreign phrase, a scientific word, or a jargon word if you can think of an everyday English equivalent. 

5. Break any of these rules sooner than say anything barbarous. 

Excerpt from "How To Write & Give A Speech" by Joan Dee