I go with place name (or significant physical features of the landscape) and the date. These never go on the front of the mat...but on the back, and on the walltag if being displayed on a wall in a show. The title is there if the viewer is interested. Just assigning numbers to images seems a bit boring to me, but works for other photographers.
Titles can be used to take the viewer one step farther than the image itself does...just as hand gestures can add to a conversation. Both can be distracting if not used carefully. Ted Orland is an example of a photographer who uses titles well.
So no rules -- just (uncommon) common sense.