Getting good depth of field with my nikkor 18-105 lens?

I'm taking family portraits of four people this next weekend. I'm wondering how to get a good depth of field with my nikkor 18-105 lens? What shutter speed, and aperture should I set my camera to in order to blur the background out? Also i'm not sure what other settings I will need to adjust. I set it to it's lowest which is f3.5 and it didn't blur anything out. Do I need to focus on an object and then take the photo. Still confused on this because i'm still learning everything on this camera.

You're probably getting f3.5 on that lense at 18mm and something like 5.6 at 105 mm. That's what you call a "slow lens," in that it doesn't let in a lot of light.

To get good blurred out backgrounds you'll need a pro f2.8 lens, or a cheap 50mm 1.8 "normal" lens. As a pro, I'd say at around $100 the 50mm f1.8 is the best investment a budget-minded photographer can make.

But if you're shooting a group of 4 people, you'd want to have some decent depth of field anyway to make sure they're all sharp (in focus). I'd use a tripod if possible and go for f8. You won't get any blurred out backgrounds, but at least all of your subjects would be sharp. That's doable with your lens.

I'd use at least a 1/100 shutter speed and a low ISO (like 200 or 250). You'll have to see what your meter says, though, and that will have a bearing on what shutter speed you use. You don't want to go lower than 1/60.

For a truly blurred out, selective-focus type shot, buy a 50mm f1.8.

Be careful how much you take from people claiming to be pros.
You could get a blurred background shooting at f/11 at 1/200 with the right distances and focal length. You don't have to be at f/2.8 or f/1.8 to get a blurred background. It helps but the Aperture you select isn't all there's to it. A smaller f/stop (larger opening) will give you shallower depth of field (the amount of the photo, front to back that is in focus). The background blurring depends on a couple of other factors. The distance from your subject to the background is one and the focal length of the lens is another. Longer focal lengths will compress a scene (make the background look closer than) while wider focal lengths can exaggerate depth. Setting the lowest f/stop you have available at your chosen focal length is a good place to start. Now increase the distance between your subject and the background your trying to blur and see what happens. Try using the middle of that lens, somewhere around 60mm then take the same shot from the same spot at 18mm and 105mm and see how it affects the background.
The only other thing to know is that some lenses render that blur better (or more pleasing) than others. By the way, it's not depth of field you're after exactly. Look up bokeh and see what you find.
Again, remember anybody can call themselves a pro.

The main aspects for out of focus:

Long focal length

wide open aperture (or nearly wide open, F4, F5.6)

Close distance to subject, far distance to background

With your lens something in the 60mm will give you an equivalent of an 85mm with film or full frame. 85mm is an ideal focal length for portraits, 60mm x 1.5 crop factor = 90mm. Have the subject stand close, and make sure any background elements are far away as possible.

here's a shot taken at F8, with a 600mm lens, you can see that the focus is gone by the tail of the bird:

http://cgipix.com/Portfolio_Anza_Borrego_Nature_Photography_Birds.htm

Family portrait… Shoot at at least 40mm, don't go lower or you get weird distortions. Shoot wide open and keep some distance from the background. Take a look at httP://www.dofmaster, com