Put 着 (zhe) straight after a verb to show that a state is continuing: the door is open, she is holding a phone, he is wearing a red top. It is a key grammar point of HSK 2.
Subject + verb + 着 (+ object).
着 goes right after the verb, before the object. It does not describe the action itself but the state it leaves behind and that is still there: 开 is to open or switch on, and 开着 means it is open or on. You will often hear 呢 at the end of the sentence as well.
Verb 1 + 着 + verb 2. The first verb with 着 tells you how or in what state the main action is done: smiling while you speak, sitting while you watch, going on foot. The main action is the second verb, so 着 goes on the first one.
Place + verb + 着 + what is there. This is a common way to say what is somewhere and in what state, a bit like "there is someone standing at the door" in English. The place comes first, and the person or thing comes after the verb.
在 before a verb says that an action is going on now: 他在穿衣服 means he is getting dressed. 着 after a verb says that the result of the action is still there: 他穿着新衣服 means he has new clothes on. To simply say what someone is doing at the moment, use 在, not 着.
A few actions, such as rain falling, can take 着 for something that is going on, often with 呢: 外面下着雨呢. Note also that 着 is read zháo in some words, for example 睡着 (shuìzháo, to fall asleep).
To say a state is not there, use 没有 before the verb and keep 着: 电视没有开着. Don't use 不 here: 门不开着 is wrong for "the door isn't open". For a question, add 吗 at the end, or ask with 什么.
The most common mistake is putting 着 in the wrong place. It comes straight after the verb and before the object, so say 他穿着红色的衣服, not 他穿红色的衣服着. With two verbs, 着 goes on the first one: 笑着说, not 笑说着.
Practise this grammar point on paper: 20 exercises using only HSK 2 words, with an answer key on a separate page. Free to print and copy for your class.
Every example on this page uses only words up to HSK 2. Paste your own sentences into the level checker to see which words, if any, are above your level.