1. Explain it simply
Verb + 过 says you have done something before - a past experience, not one specific finished event: 我看过那个电影.
To say you have never done it, put 没(有) before the verb: 没 + Verb + 过. Keep 过 in place.
To ask, add 吗 at the end, or put 没有 after the phrase: V过…没有？
2. Show examples
我看过那个电影。
Wǒ kànguò nàge diànyǐng.
I have seen that movie.
experience
我没去过北京。
Wǒ méi qùguò Běijīng.
I have never been to Beijing.
没 negation
你喝过中国茶没有？
Nǐ hēguò Zhōngguó chá méiyǒu?
Have you drunk Chinese tea (or not)?
没有 question
你去过中国吗？
Nǐ qùguò Zhōngguó ma?
Have you been to China?
吗 question
3. Share a tip
过 marks an experience ('have ever done'), while 了 marks a completed event: 我看过那个电影 means you have seen it at some point, but 我看了那个电影 means you finished watching it at a specific time. To negate 过, always use 没 (never 不), and leave 过 in place after the verb.