1. Explain it simply
太 goes right before an adjective, and 了 goes right after it: 太 + adjective + 了.
It can mean 'too (much)' in a complaint, or just 'extremely' as strong praise.
2. Show examples
这件衣服太贵了。
Zhè jiàn yīfu tài guì le.
This piece of clothing is too expensive.
太 + 贵 + 了
今天太热了。
Jīntiān tài rè le.
It's too hot today.
Describing the weather
这个电影太好看了！
Zhège diànyǐng tài hǎokàn le!
This movie is so good!
太…了 as enthusiastic praise, not a complaint
3. Share a tip
Don't drop the 了 at the end - 太贵 alone sounds unfinished. 太…了 is a matched pair.