ALWAYS bookmarks! Have a beautiful collection of them, consisting of purchased ones, down to a TAA Bar List, & every type in between.
I NEVER 'dog ear' a page! That's disrespectful to a book, & I love books!
If I've a marked book, I press it, & that gets it nearly back to right.
NOT having a bookmark, ready, at the back of the book is just plain, straight-out laziness!
A train ticket, a piece of paper, a Woolies docket,
ANYTHING can suffice as a bookmark!
If I've an oversupply, I donate to Library, as they give them to house-bound persons, when they take Library books to them.
When I worked, used to carry some of my oversupply in my briefcase, & give to people on train, or at work, if I noticed they had no bookmark! Much better than 'dog-ears'.