With any given focal length DOF is a function of two variables.
1. Aperture....shoot aperture priority and try 2.8, 4 and 5.6 and use the one you like. Smaller holes give you deeper DOF. Your eyes' pupils constrict (accomodate) when you focus closer.
2. Camera to subject distance. The closer you are the shallower DOF you get.
3. You get a third variable with a zoom....focal length. Longer FL has shallower DOF.
Changing ISO will give you a wider range of setting possibility, of course, sans a direct DOF effect.
Big DOF:
Little DOF:
Bill s right....shoot several shots playing with the variables. Choose the one you like.