If done properly in a story that can benefit from such, I think chapter titles are a great idea. They can function as brief "teasers" for the reader of what is to come in the following pages, and they work especially well for stories that jump around in time, but there are certainly exceptions to any rule.
I also find chapter titles to be tremendously helpful for recalling sections of a book, for when the reader finds it necessary to dig up information at a later date. If the novel or series contains a Table of Contents, then this will further facilitate that process.
For the guy(s) asking about knowing when to intelligibly divide chapters and/ or scenes, I will never profess to be absolutely certain either, but I can at least throw in my two cents on the matter.
I generally have scenes that just float around in my mind, and (hopefully) the connecting of them all creates a novel. Though maybe not vital, for me each of the scenes must present a problem and a resolution, so that each scene is essentially a short story in itself. Sometimes these problem/ resolution combinations may be carried over from or to other chapters, but they are assessed in a different light so as not to be redundant.
I also wish to emphasize that a conclusion for each scene does not necessarily equal a clean break; I have had situations in my own writing where a chapter is actually ended abruptly by a surprise intervention of dialogue (for a boring example, a messenger running up) or a physical confrontation/ attack. This can then segue into the next chapter rather easily, or the writer can take liberties here and jump around in time, which is probably both cruel and to my liking.
My only other immediate thought is this: make sure every scene and every chapter serve some purpose in developing character or advancing the plot of your story! If a particular section does neither, strongly consider eliminating or reworking it to make it satisfy one or both of the above requirements.
Other than that, it pains me to say that chapter and scene breaks should just "feel natural" to the author and do not necessarily call upon hard and fast rules in order to be properly executed. I am often reminded of Stephen King's
The Shining for the simple reason that this lengthy book contains a very brief chapter (maybe only half a page or so) amidst a number of other chapters that consist of numerous pages.
Cheers,
WD