Garden bed design preferences can be a very personal thing.
Much is pre-determined due to the lay of the land. Most beds are either border beds (they have a back-drop or can only be viewed from one side) or Island beds (which can be viewed from all sides). Bed shape and distribution should be proportional with your property, and will also vary depending on your preferences.
Generally, about 4 feet is the maximum width of a border bed, if you want to be able to reach from a pathway, or you will have to create access to the center of bed. Paths or stepping stones can be used for this. Raised beds have advantages, depending on your soil, aspect, and other personal preferences. Very high beds can make jobs like weeding more comfortable because you do not have to bend over as far to reach the ground level. Give Oakstead a call if you need some help with design or construction.