Even though I'm new to digital scrapbooking, depth of field is something I've been exposed to (sorry for the pun) for about 20-25 years. The way I can remember about depth of field is comparing it to playdough being extruded though an opening. (Or spaghetti if you prefer.) The bigger the opening (f-2, 2.8 etc) the more likely the dough is to plop out in one piece -shorter depth of field. The smaller the hole (f 8, 16, 22 etc.) the longer the rope - longer depth of field.

I've had instances over the years when I used f2 or so where I've focused on a person's eyes, I thought, and actually the end of their nose was in focus and their eyes not. The "rule" for portraits is f5.6. Keeps the eyes and nose in focus but the background will be blurred nicely. With landscapes a long depth of field works well when you have foreground clear to background you want to stay in focus. F22 will keep them all in focus but even f8 and higher will work well too.

I have a Nikon D-70 and love it!
Ann