在听、说、读、写四种基本技能中，“写”对英语学习者来说可能是最困难的。要提高“写”的技能只能通过写，有人说 “Learn to write by writing”就是这个意思。
一般来说，写日记可以起备忘作用，在回顾往事时能够有所依据。更重要的是写日记还可能锻炼意志，培养恒心，提高写作能力。十九世纪俄国文学家托尔斯泰把他自己的成功秘诀归之于坚持写日记。作为英语学习者来说，用英文写日记也是提高写作能力的好办法。
日记通常是一日一记。可以写你的生活趣闻，学习心得，社交活动……总之，凡是你认为值得一记而又能用英文表达的，都可以记下来。这种日记可长可短——有事则长，无事则短，但是不要“三天打鱼，两天晒网”。即使是没有什么好记的，你写上两个字“Nothing particular”也是好的，因为这样做就锻炼了你的意志，培养了你的恒心，而且提高了用英语表达的能力。
写英文日记也有一定格式，这主要指日记的开头。日记开头总是先写日期、星期和气候情况，通常从正文上一行的顶格处写起。日期的顺序可以是“日、月、（年）”，也可以是“月、日（年）”；星期可以写在日期之前，也可以写在日期之后，还可以干脆不写；天气情况（如fine, cloudy, windy, rainy等）可以紧接在日期之后写，也可以写在第一行的最右端，还可以干脆不写。
例如：
Tuesday, March 28, (2001), cloudy
Tuesday, 28th March, (2001), cloudy
March 28, (2001), Tuesday (cloudy)
日记的正文是日记的主体部分，写在日期的下一行，可以顶格写，也可以内缩3—5个字母。正文的文字不求华丽，但求简单明了。因为日记所记载的事常常是当天已经发生过的事情，所以谓语动词通常用一般过去时。有时为了简洁，第一人称主语（I）还可以省略。
例如：
Wednesday, Nov. 20. Rainy
(I) Didn't go to school because of illness. Mother told me I had got a bad cold. I took some medicine and drank lots of water. (I) Stayed in bed the whole day. Later in the afternoon, I began to feel better. (I) Think I'll be well enough to go to school tomorrow.
下面这篇日记引自许国璋《英语》第一册，它记述了学生下乡帮助农民秋收的活动，略有修改：
October 24.
Today we began harvesting. We got up at daybreak, and after an early breakfast we started off for the rice fields. We got there after half an hour's walk.
The fields around us looked like a golden sea. I have never seen anything so beautiful! We worked side by side with the commune members. At first some of us worked rather slowly. The peasants showed us how to reap the rice and how to enlace the bundles. Soon we learned to work faster.
We worked in three groups. "Faster, faster! We mustn't fall behind the others!" That was the thought in everybody's mind.
Evening came before we realized it. We put down our sickles and looked at each other. Our clothes were wet with sweat, buy every face wore a smile.
We harvested thirty mu altogether. That was not bad for the first day. Tomorrow we shall certainly do better—much better.
下面这段摘自《德希蕾日记》的第一章，时期是1794年3月，没有具体日期：
……
Last November I was fourteen. Papa gave me this diary then for a birthday present.
“What shall I write in it?” I asked him. It's a beautiful diary, but the pages are rather large.
Papa smiled and kissed me. “Write the story of Mademoiselle Desiree Clary1,” he said. Then a worried look came into his face. Since our great revolution2, he has often had that look.
A few days after my birthday, Papa suddenly died. So I haven't been wri?鄄ting my diary; I've been too sad. But I'm starting it tonight because I'm too worried to sleep. The police arrested my brother Etienne today. Tomorrow I must go to the Town Hall with his wife, Suzanne. We must try to save him. If we fail, perhaps he'll be guillotined3. It's a terrible thought...