First, stone carving. For example, many walls and rocks of various places of interest have poet's handwriting.
Second, poetry collection. Poets are not necessarily poor, such as Yan Shu and Nalan. And the poems they wrote are all their own collections of poems.
Third, oral communication. Just like singing, you don't have to read the lyrics to sing, but you may just listen to others sing.
Fourth, sort out the comments of future generations. For example, Wang Guowei loves to do this. Put the poems together and add your own feelings.
Five, national preparation and promotion, this is the most important channel. For example, The Complete Poetry of Tang Dynasty was written by Emperor Kangxi of Qing Dynasty who personally ordered Jiangning to weave, that is, Cao Xueqin's grandfather, on the basis of Hu Zhenheng's Tang Yin Tong Qian and Ji's Tang Poetry in the late Ming Dynasty. Emperor Kangxi also personally prefaced it. After the founding of New China, a large number of ancient poems were collected and sorted out, which also played a decisive role.