For me, this is where the fun begins.
I like to layout my garden shape by using a hose or a rope to define the outer edge. Try to incorporate large sweeping curves whenever possible, this adds grace and visual interest. Follow by cutting a smooth edge with a scalloped edger.
At this point, if you have grass that needs removal this is the time to do that. I prefer to set the grass to the side for use later.
The double digging method of prep is my favorite. I start by using a pick to loosen the soil (in my area it is as hard as concrete, and this is the easiest method). If you have big strong kids, this is the perfect job for them. Then start digging — go down one shovel-full, set aside, dig down one more shovel-full, set aside. This is a huge amount of work, but will pay off with a deep, wonderful bed.
Once you have dug out the bed completely, you can start reloading it. First, by putting the grass layer back in, but, put it in upside down. The grass will break down into nutrients for the garden. Next, layer in the soil you removed, adding any amendments you need, breaking up the soil into a smooth texture as you go. In my location, I always add compost, grass clippings and sand, but in your area this may be different. Let the garden rest for a couple of days, then with a spading fork, give it one more stir. At this point you have the most luxurious garden bed you could ever ask for. Next up: plants!