I get most of my books from the library so i can't dog ear. I use postit note lots because i can not only mark the page, but where on the page i was reading. I also will use pictures as bookmarks cause i can see my nefew everyday then.
I almost always read chapters at a time, so usually I just try to remember what chapter I'm up to, although sometimes when I stop short, I just stare at the page number and hope it sinks into my brain.
I hate to dog-ear my books I think it kinda ruins it, I like things to look pretty. Its just one of those things. I just use anything to bookmark my books, anything from a real book mark to just a bit of paper I found at the time.
If it's a book I'm reading for fun, I will use a bookmark, regardless of whether it is mine or the library's. If it's a book I have to read for class, assuming I own it, I will dog-ear, since chances are I'm writing all over it anyway. Books that are meant for studying or analyzing just don't get the special treatment, sorry.
Always bookmarks... to dog ear makes a permanent crease that eventually becomes a tear. I hardly ever use bookmarks as my family changes the pages around as a terrible prank on me. So I have to just remember the pages of my books.
dog-earring seems a bit disrespectful to me. its like ripping a page out or something like that.
before i discovered books' awesomeness, i folded the pages down, but now i care too much.
however, permanently marking memorable passages might be worth the worn out look...
its fun to find scraps of paper for specific books and then leave them in the book for the next read.