Hi Lorraine,
The Pillow Book by Sei Shōnagon, a court lady to the Empress Consort in the Heian period, is one of the most famous of this style of writing, the zuihitsu (assorted writing)
In answer to your question, perhaps it could be said that you can mix poems in the narrative just as Sei Shōnagon has done in her book. Her narrative is full of descriptions of the court ceremonies and politics observed in the rise and fall of various officials and their lineage, the clothes, the household rites, the seasons, the pilgrimages and of course the courtships and rendezvous of the ladies and nobles of the court. The tone is intimate not quite as gossipy as Diary of Bridget Jones but has quite revealing details. Her own opinions on the people and the events are a vital part of the account. It was customary in the Heian period for lovers to exchange waka poems and her book does have some poetical passages and titles of paragraphs/chapters.
She regarded Murasaki, the author of Tale of the Genji as her rival and therefore the tone of her account is not as shot through with mono no aware as Murasaki's work but still immensely engaging and enjoyable.
"Assorted writing" is perhaps the key to the zuihitsu style or form.
light pilgrim