Garden Bed | Garden Path: Design your Garden to Fit your Body
You've got your graph paper, rulers, pencils, and a 28 sticky notes coveting special items in your seed catalogs, but you're stuck... How does one draw a garden plan? How big are things anyway? Lumber tends to be 8 feet long, but is that the right length for anything beyond drywall?
Sizing & Garden Path Design
Whether your bed edges form sweeping curves or crisp, straight lines, the paths between them will still fall into two primary sizes in the garden:
Big is two or three people wide, or perhaps a person pushing a bicycle or a two wheeled garden cart,
and
Small is one person holding a trowel or a hoe. If you have a lawn, small is the width of your mower. Exaggerating the difference in garden path design sizes provides structure to the garden by clarifying what sort of experience a gardener or visitor is intended to have in each space.
If you are working on less than an acre (and most of us are), you need just one grand path, and can perhaps have a second, but no more than that.
These mini-avenues are the best candidates for a distinctive path surface, perhaps pale gravel or sand or brick. Any smaller garden paths are best left to blend in a bit more. If a distinct material is used, it should be more earthy and less visually obvious than the grand path. (The interplay created by using different materials to surface different paths is key to an herbal Knot Garden.)
Sizing & Garden Bed Design
The sizing of garden beds is related to the fringe of the bed, not the center. The center may be planted with something that will grow unencumbered, something that will need neither babying nor harassment. The edge is the portion the gardener works on more regularly. Vegetable garden beds are often thought of as being entirely "edge" because the farmer / gardener will spend so much time transplanting and harvesting.
Few people can comfortably reach more than 30 inches, so few vegetable beds are wider than about 4 feet, and that only when accessible from multiple sides. The bed on the left is accessible from multiple angles: the yellow front strip from the primary garden path, the white U from the thin garden path, and the blue side zones from the lawn flanking the garden. (Bright yellow areas are accessible from both white and yellow zones, the green squares are in both the yellow and blue zones.)
Where I live, a gardener would plant basil (an annual plant here) in that incredibly accessible green zone for a super easy grab-and-go set-up. Rosemary (a hardy shrub here) would be suitable in the more remote blue zone, because access to clipping is still available but there's no need to muck about in rosemary's root zone once it's established.
Garden beds are also sized to maximize the happiness of the plants, encouraging them to produce bountifully. It all comes down to happy roots: roots are happier when you aren't stomping on them! (actually, me too!)
By working path-row-path-row-path..., valuable garden soil is given over to the compacting and damaging weight of the gardener. A wider bed maximizes the space given to the plant roots while minimizing the soil the gardener is walking on.
Can you still plant in rows? Sure, just make the bed two or three rows wide: path-row-row-path-row-row-row... If you do have an out of reach center, put down one or two stepping stones for those rare times when you do need to prune or water.
Bonus hint: offset the plants in adjacent rows. This keeps the distance between plants, but lets the rows be closer together.
Further Reading: Vegetable Garden Layout talks about using paths to define the center and edge of a garden, and touches on finding appropriate materials to coordinate with the rest of your site, and
Herb Garden Design has a section on Knot Gardens, for which good garden path design is crucial.
Whether your bed edges form sweeping curves or crisp, straight lines, the paths between them will still fall into two primary sizes in the garden:
If you are working on less than an acre (and most of us are), you need just one grand path, and can perhaps have a second, but no more than that. 
Bonus hint: offset the plants in adjacent rows. This keeps the distance between plants, but lets the rows be closer together. 
