http://www.tested.com/tech/photography/461060-living-photography-angling-plane-focus/

I ran into this article and thought that this might be helpful for beginners who are trying to get narrow depth of field. Imo doing this improperly and not using wide enough dof are one of the most common beginner mistakes. Even if you want a narrow dof, you really need to check that all things you want in focus fall into the focused area and shooting something with 50mm prime wide open usually results in too small dof, just by raising the F-value with 1/3-1 step can make a huge difference without sacrificing too much of that bokeh people are after.