The spot chosen should get as much sun as possible. If the soil is at all heavy it will be necessary to improve the drainage. This is done by digging out an area one foot deep and mixing in a layer of stones, broken bricks or gravel into the subsoil.
Remember Hugulkultur in creating raised beds. Since I like the higher beds, filling the bottom half with prunings and such will reduce amount of topsoil needed to fill bed.