This garden is much to large to give it a full make-over in one day, but an obvious problem that can be tackled is the north facing wall. This forms the main view from the patio/sitting area, but is totally devoid of anything nice to look at. The rest of the garden is clearly being dragged down by this one feature. 

Some of the plants in the corner by the garage are also wrong in that they need sun rather than shade and are planted too closely together.