The overall style of your landscape should be determined by two factors: your own taste and what makes sense within the context of your property.
Although your garden should be a distinctive expression of you, it should also be in harmony with its surroundings. For example, a picket fence with flowers spilling out between the slats may be perfect for a traditional-style home with a symmetrical faade. But that homely style would look out of place in front of a contemporary building.
The scope for various style possibilities is vast, and can always modify an existing style to better represent your requirements and situation. For example, you can soften the clean, straight lines of a formal garden by allowing plants to intertwine and spill onto pathways.
If you like Japanese gardens but don't want the precision design typical of that style, you can introduce elements from conventional Japanese gardens, for instance; stone lanterns or basins can be used to instantly evoke the Japanese motif.
Characteristic elements of formal design include straight lines, geometric forms, symmetry and central axis, usually leading to the house. In a larger garden, there may be several axis that link the different areas. Because formal gardens have a strong sense of structure delineated with hedges, walls and paths, they are usually interesting and striking throughout the year. This type of garden is much less dependent on seasonal blooms for its beauty than other garden styles.
Informal gardens are designed with curving, instead of straight lines. The idea is to mimic nature rather than force it into unnatural shapes and forms. Curiously, it can be much more difficult to create a well-designed informal garden than a formal one, perhaps because informality is a newer design form and the concepts are more abstract and challenging. What looks right and pleasing to the eye is less obvious in an informal garden.
Most of the same principles that govern formal designs apply to informal gardens, with the exception of balance and geometry. Instead of working with straight lines, you are designing with loose, flowing forms rather than tight, sharp zigzags.
On large and even moderate-size properties, you can include two or more different garden styles if you divide up the space into distinct garden zones.
For example, next to your house, you can have a patio which can be enliven with pots and hanging baskets spilling over with colorful annuals. To one side of the patio, you can create a Japanese garden vignette, including bonsais, a few bamboo plantations, a dry pond and few rocks.
A steep slope could separate the level patio near the house from a lower garden that could contain drought tolerant plants growing in delightful profusion. A Chinese pergola could also be well positioned in the garden.
Whatever style you choose for your property, your landscape will be more beautiful place when it is in harmony with the constraints and assets of the climate and topography. While you need not only use only native plants, at least try to select plants that are well adapted to the region.