How to get a shallow depth of field on a Nikon D5200 with 18-55mm lens?

Hi and thank you for reading and answering this question (if you decide to do so)

Problem:**I have tried and tried and failed, and failed to get a shallow depth of field in my images, actually I lie, I got it once but can't recreate it, and that once the background isn't too blurry, just a little.

I have studied online for hours, and watched continuous videos - still nothing. I kind of understand the concept, as in the 3 requirements for shallow DOF (shutter speed, Aperture, ISO) though still can't get that pro looking shallow depth of field (DOF) image.

***Settings I'm Using:
I'm not to sure about other DSLR cameras (as you can tell i'm not a pro) though on my Nikon D5200, I use the A setting on the dial (you can change aperture manually and camera auto changes shutter speed), my lens only allows a min aperture around f3.5, with ISO @ 400 (from what I learned this is the recommended 'safe' ISO setting). I'm then close to my subject (as in whole face covers/in frame, or sometimes a tad further (head and shoulders in frame. Though still no shallow DOF.

SO… Does anyone here own a DSLR and know how to get a great shallow DOF when they want it, on demand! Lol. And does anyone know what I'm doing wrong?

You can only open the lens to maximum, if your largest diaphragm is 3.5, then set your camera on A and set the maximum aperture. If you want more bokeh, you need a more open lens, in the 1.8, or 1.4, even down to 0.95 lens. A huge and cheap lens for that is Sigma 30-1.4.give it a try. Some 2.8 Zooms do good, Tokina 11-16 for example. If you know how to focus manually, try Samyang lenses, some open wide and are excellent in IQ. The larger you open, the shallower your DOF gets and the better your Bokeh.

http://www.pbase.com/lou_giroud/sig3014

http://www.pbase.com/lou_giroud/image/146798683

on that link you get an idea of shallow DOF with the sigma 30-1.4. If you surf around, you can see other lenses, like the Nikon 50-1.8 that produces same good DOF. All is how much you want on the shot, 30, 50, 75-80 are all good for portrait. Smaller is better for landscape, longer better for portrait, but all do the same good job if the can open wide.

You've studied well, but you've left out one factor, and that's focal length. A wide angle lens gives more depth of field, and a telephoto lens gives less.

If you shoot at or near the 18mm focal length, you'll maximize depth of field. To get the shallowest DOF, shoot at 55mm, and at f/5.6, the widest aperture you'll have available at 55mm.

For true shallow depth of field, you'll need a different lens. One of the most reasonably price lenses for that would be the Nikon 35mm f/1.8 AF-S. It autofocuses with your D5200 and will give you amazing bokeh (shallow depth of field).

Here's some examples using this lens for you.
With a D5200:

With a D5100:

The lens (one of my favorites) is under $200 on Amazon.
http://www.amazon.com/...001S2PPT0/

Here is a website that might help:

http://www.althephoto.com/concepts/selectivefocus.php

The main issue you have is your lens. It is not the best lens for a shallow DoF. A longer focal length or a faster lens, or a combination of both is highly desirable. Maybe it's time for a new lens?