Five Shades of Do: 做／办／干／搞／弄

1. 做 

e.g. 他在做饭呢。

做 means to do, to produce, to engage in. 

• 做事要认真。
• 我得多做运动。
• 我在做作业呢。
• 他做了一首诗。（做 means to write and compose in this case.）
• 晚安，做个好梦。

2. 办

e.g. 他今天出去办点儿事儿。办事（ban4 shi4）means settle something or issue. 

• 他正在办公，请小声点儿。办公 means.doing work related to one's job position, not homework, not house work.
• 他去办签证了。He went to get a VISA. 
• 请您在这儿办手续。办手续 means handling the procedures，etc。

3. 干

e.g. 今天大家干得真不错。
The meaning of 干 is to do some task. It refers to the literal action of doing somethings, which is more colloquial and informal than 做。

• 他在干活儿，不能和你玩了。
• 你在干什么？我在干家务。
• 他干翻译工作干了几年了？(Here 干 means to be engaged in some work or to be in charge of something, like 他干过服务员。)

4. 搞

e.g. 他搞这种工作很有经验。
搞 means to do or carry out something，如～卫生、～家务、～计划等。干 and 搞 are sometimes interchangeable，but 搞 has a wider range when referring to certain actions difficult to describe concretely， 如搞对象、搞运动等. In these cases, 搞  means "to engage in" and "to take part in" and it can not be replaced by 干.

e.g. 他朋友是搞体育工作的。
搞 means to be engaged in a certain type of work，如～生产、～艺术等。The difference between 干 and 搞 is that 干 implies taking some positions, while 搞 does not. 

e.g. 他搞到了两张足球票。
Here 搞 indicates to manage to get，如～水、～钱、～汽车等。干 has no such meaning。

5. 弄

e.g. 他家里弄得很整洁。
弄 means to do something，如～饭、～菜、～卫生等。Both 弄 and 搞 can be used to refer to actions difficult to describe concretely, but sometimes their objects are different. 弄 in ～孩子、～电器 means to take care of and repair respectively.

e.g. 他弄着了一套新房子。
Here 弄 means to manage to obtain，如～车、～票、～护照等。

e.g. 他喜欢弄花儿养鸟。
Here 弄 refers to playing with something carelessly or playing a trick，如～手段等。

Summary

1. 我还有几件事要办/做。 办 and 做 basically carry the same meaning and they are formal.
2. 我还有几件事要干。干 is less formal than 办 and 做, but you can use it in most of the occasions.
3. 他是搞计算机的。 Here this 搞 = 从事于（engaged in）computer business or industry but sometimes 搞 can express negative meanings like 他把工作搞得一团糟 he screwed his work, we usually use this as a fixed collocation: 搞得一团糟Gǎo dé yītuánzāo.
4. 他马上就要弄好了，不要急。It is very casual to use 弄.
5. 他把这个桌子弄坏了.  You can see "弄坏了" as a fixed collocation, means broke something.

Practice: Please fill the blanks by using  做, 办, 干, 搞, or 弄.
1. 他现在没有在这里______公，他去______护照（hùzhào）了。
2. 他在______什么？他在图书馆______作业。
3. 他把今天的工作______完了。
4. 我把电脑______坏了。
5. 他们两个在______对象。
6. 我______到了两张电影票。
7. 她的男朋友是______化工的。
8. 哎呀，你怎么把这里______得乱七八糟 (luàn qī bā zāo)？
    赶紧去______干净。
9. 他肚子饿了，______了一点儿面包吃。
10. “你在______什么呢？” “我在______实验，等我______完了，我给你打电话。”



Reference:
http://chinese.stackexchange.com/questions/12290/differences-干-办-做-搞-弄

http://lang-8.com/450372/journals/280788679208591218130229342507864399460