This word is used in so many different contexts. It becomes rather confusing.
What is a good way to distinguish the different situations in which this word is used?
1 Answer
As a native Chinese speaker, I would think twice if I see "着" in ancient Chinese or in genteel writings. It is a hard character to learn. But the most common usage in modern Chinese, especially casual and oral occasions, is "function word"(虚词). It gives a hint of the mood and tense of the sentence but does not have a concrete meaning.
To make things clear, I would quote Modern Chinese Dictionary(《现代汉语词典》)'s full explanation but give my own comments to each meaning.
着【zhāo】
1 （～儿）（名）下棋时下一子或走一步叫一着：高～儿｜支～儿。
2 同“招”。
3 〈方〉（动）放；搁进去：～点儿盐。
4 〈方〉（动）用于应答，表示同意：这话～哇！｜～，咱们就这么办！
Comments: None of these meanings are common.
The first two are noun uses. Both are gradually substituted by "招" -- whether in chess play or not. A strict editor may correct you and use "招". The only case is in the proverb “一着不慎，满盘皆输”, only the original "着" is correct.
3 & 4 are northern dialect, around Beijing I believe. Very very rare. I've only heard this expression in TV series about BJ life in the last century. I can't think of any other cases.
着【zháo】
（动）
1 接触；挨上：上不着天，下不着地。
2 感受；受到：～风｜～凉。
3 燃烧，也指灯发光（跟“灭”相对）：炉子～得很旺｜天黑了，路灯都～了。
4 用在动词后，表示已经达到目的或有了结果：睡～了｜打～了｜猜～了。
5 〈口〉入睡：一上床就睡～了。
This is the most confusing pronunciation I believe. The neutral tone "·zhe" is the most common one and this is the second most.
There are some fixed combinations: “着调”(1)、“着凉”(2)、“着魔”(2)、“着迷”(2)、“睡着”（4&5）、“点着”（related to fire, 4). In these cases, you are almost certain it is "zhao2" not "·zhe".
Also when it's "verb+不+着" or "verb+得+着", it must be "zhao2" not "·zhe".
For 1, it is used as an active verb, not a functional verb, so it is not following a real verb. It means “挨着”、“够着”, "reaching". But it is also a very rare usage.
着【·zhe】
1 （助）表示动作的持续：他打～红旗在前面走｜他们正谈～话呢。
2 （助）表示状态的持续：大门畅～｜茶几上放～一瓶花。
3 （助）用在动词或表示程度的形容词后面，加强命令或嘱咐的语气：你听～｜步子大～点儿｜快～点儿写｜手可要轻～点儿
4 加在某些词后面，构成介词：顺～｜沿～｜朝～｜照～｜为～
This is the most common usage in Modern Chinese. When you see “着” following a verb and not with a “不”(or "得"), most likely it is a neutral tone "zhe".
However, this usage does not exist in ancient Chinese / classical Chinese （文言文）.
着1【zhuó】
1 穿（衣）：穿～｜吃～不尽。
2 接触；挨上：附～｜～陆｜不～边际。
3 使接触别的事物；使附着在别的物体上：～笔｜～眼｜～手｜～色｜～墨｜不～痕迹。
4 着落：寻找无～。
着2【zhuó】
1 (动)派遣：～人前来领取。
2 公文用语，表示命令的口气：～即施行。
This part is very confusing for Chinese pupils as well. There are many fixed combinations under this usage as well.
For "着2", it is most often in "着人", meaning "sending someone", but a more polished way than “派人”. Not your first choice of writing or speaking but you might see it in some places.
For "着1", I would suggest you just remember the following words: “着笔”、“着力”、“着陆”、“着墨”、“着色”、“着实”、“着手”、“着眼”、“着重”；“沉着”、“附着”、“胶着”、“衣着”、“执着”
Yes, there are more words to remember... so if you see a "着+noun" pattern, "zhuó" is more likely than "zháo". Also, people are using both pronunciations interchangeably in many words. Here I listed are the ones I believe not quite proper for the other pronunciation.
For "verb+着", here are the very few fixed combinations you can only use "zhuo2". If it is after a word meaning "stick", use "zhuo2"
Notes:
"执着" can be written interchangeably with "执著"
"穿着" can be "chuan1 zhuo2" or "chuan2 ·zhe". "chuan1 zhuo2" is a noun, or an intransitive verb, e.g. 他的穿着(n.)很时髦；他穿着(v.)入时. "chuan1 zhe" is a transitive verb, e.g. 他穿着时髦的衣服。
This answer is getting super long.
So my ultimate rules are as following:
"verb + 着" is most likely "·zhe", especially when it is used as a transitive verb. Remember some of the "zhuó" combinations, and when it's about clothing or sticking.
"verb + 不 + 着" and "verb + 得 + 着" are "zháo". "睡着" is always "zháo". "Reaching" is always "zháo".
"着 + noun" is most likely "zhuó". But remember the "zháo" combinations. The line between "zhuó" and "zháo" in this form is a bit vaguer.
I hope this long answer can be somehow helpful. I'm a native Chinese speaker, but inexperienced in explaining Chinese in English LOL. Let me know if anything confusing.
