With my dad, he had a period of 1 week during his final weeks when his energy rallied and he wanted to talk about his life. So I video recorded him. That's the biggest thing, really, to have videos of them talking. He talked and I asked questions, and I heard some stories from his life for the first time. I got videos of him telling the story of how he met mom, how he courted her--they're priceless to me and I think the process was therapeutic for him as well.
With my mom, she wasn't big on talking about her life. We spent a lot of time holding hands and sitting together. I played soothing music to her. Wish I'd thought of the idea of reading to her.
Dad liked to be surrounded by loved ones, so we had his siblings and other people visit. Mom was the opposite. She didn't have the mental energy to deal with friends and non-immediate family, and we had a lot less people come to see her.
Dad's decline was more gradual, spread over several months. Mom's was much more sudden, and from the time we realized it's beyond treatment to her passing was a matter of weeks. As hard as it was, have the conversation about their wishes and will sooner rather than later. Mom had to sign a bunch of documents mere days before her passing and it was physically very difficult.