I listen to a lot of audiobooks, read a lot of library books and e-books, still somehow never have enough room on my bookshelves.
If i have strong feelings, I tend to write a review almost immediately on finishing a book. If I'm ambivalent on a book, I wait a couple hours so I've had time to think about it. If I don't really have a strong opinion, I may wait until next time I'm on booklikes anyway and just do a short note.
I'm curious what everyone else does.