过 (guo) goes after a verb to say that you have done something at some time in the past: you have been to China, you have eaten dumplings, you have met someone. It is a key grammar point of HSK 2.
Subject + verb + 过 + object.
Put 过 straight after the verb. It is said with a neutral tone (guo). The sentence tells you that this has happened at least once in your life, but not exactly when. In English this is usually "have done" or "have ever done".
To say you have never done something, put 没有 before the verb and keep 过. This is different from 了, which you drop in a negative sentence.
The most common mistake is to use 不. 我不去过中国 is wrong: 过 is always negated with 没有, never with 不.
Add 吗 at the end, or end the question with 没有. To answer yes, repeat the verb with 过, as in 去过. To answer no, say 没有, or 没有 with the verb and 过, as in 没有去过.
了 tells you that one action happened or that something has changed. 过 tells you about an experience. 他去中国了 means he has gone to China and is probably there now. 他去过中国 means he has been there at some point and is not there any more.
You can add a time word or a number of times to a 过 sentence when you want to say a little more about the experience.
过 never goes at the end after the object. Say 我学过汉语, not 我学汉语过. With verb-object words such as 见面, 过 goes between the two parts: 见过面.
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.