Louise
The basis for achieving good focus in the image from front to back is an understanding of the principles of hyperfocal distance. But it has to be said that some people do not really think it is that important and work to the 'rule' of focusing one-third of the way into the image. That is a perfectly good 'rule-of-thumb'. However, I feel that for an image such as this, it is relevant to understand and apply the principles of hyperfocal distance. In this image, given that I was working at 24mm with an aperture of f11 on a Canon 40D, which is a 1.6 crop factor camera, the hyperfocal distance was just slightly under 8'6" (for those of us who still work in imperial measurements).
I would point you towards a couple of resources to get a good understanding of Hyperfocal Distance.
Here on CiC and
here on an external website.