There are three steps to doing this correctly:
1) Adjust the binding to the boot sole length and ensure that the forward pressure indicator is within range. Each binding manufacturer has a different way of indicating that the forward pressure is correct, so I can't give precise instructions here. But I will say that if you get the forward pressure wrong, nothing else will be right and the ski may come off when it's not supposed to or not come off at all. This is the step most people miss when doing their own bindings - it's not rocket surgery, but if you don't know how to read the forward pressure indicator, find out or take the skis to someone who does.
2) Look up the DIN in the DIN chart ( http://www.dinsetting.com/images/MarkerDinChart0708_sm.jpg ) and turn the screws to the right number on the heel and toe pieces. A shaved monkey can do this. Don't fall for the common misconception of thinking you know how to adjust bindings just because you can do this step.
3) Test the bindings by applying torque and noting that the binding releases at the proper torque. The torque is the number in the last two columns on the chart. For me, it's 58 Newton-meters to release the toe and 229 Newton Meters to release the heel. Don't have a torque wrench calibrated in Newton-meters? Well, the ski shop does and will only charge you ~$20 to test your bindings.
My advice is that if you're only doing it once a season, just take it to a shop and be done with it. If you're planning on changing them out on a regular basis, learn how to read the forward pressure indicator and do it yourself, recognizing that your wife or son will be skiing on untested settings. My take is that if the forward pressure is correct and the binding has been tested recently you should be fine. I have demo bindings on my skis and loan them out sometimes without testing them each time. I figure that if this is good enough for the demo hut, which doesn't test each time they send out skis, it's good enough for me.