Garden Space
Once you have you know how you want your outdoor spaces to function and have an idea on how to divided them up, you need to come up with a specific plan to do so. Here are some things to think about:
Garden wall - There is nothing like a solid barrier to stop noise, and give privacy. A garden wall could be as low as two feet or as high as six, but higher walls tend to feel more like prison walls than garden walls unless they can be softened with plants. When the garden area is elevated from the street a lower wall can provide a high level of privacy, while still allowing the outside to be seen.
Garden seat/serenity garden - a quite corner of the yard makes an ideal serenity garden: a place that it highly private and quite, where you feel like you've escaped into nature. Add a view into the serenity garden from a kitchen, bedroom or office and it can be appreciated all year long.
Places on the edge - people generally prefer to sit on the edge of a space with their back against something rather than in the middle, so a sitting area which does this is more likely to be used. Create sitting areas up against the house, or against walls or shrubbery when possible. Any space that is inviting will eventually become uninviting unless there is a place to sit down. Not all seats have to be on the edge, as other criteria may make a place also desirable, like a perch up off the street, or place that for other reason feels protected enough. People will make use of anything that will function as a seat, including rocks, stairs and garden walls, so allow that to happen: in fact encourage it. Outdoor spaces should have a variety of sitting places, so that each space can be enjoyed. When the steps to a house are surrounded by "shoulders" (short, wide walls), they will almost universally be sat on.
As a general rule, people want to feel protected, but still in view of the action.
Build in 3D - its much easier to build a garden when you're standing in it then on paper, because you can actually experience what the spaces feel like. It's still good to have an idea on paper, but it's also good to be flexible and keep an open mind. A garden built by actual experience is bound to be better than one built only by a paper design.
Path shape - although it is counter intuitive, the shortest path isn't the best path: rather the best path has curve to it. Surprisingly people don't mind walking a bit longer, as long as the curve isn't ridiculous (you can find poor path layouts in many parks and college campuses). Nor does the path need to be the same width: it can narrow and have bulges. When the path is to the front door you need to make sure you don't hinder anyone moving furniture in and out, and if there is to be handicap access you need to eliminate stairs also.
A curving bulgy path not only looks better, but it adds a sense of separation between the house and the street, without making the house uninviting.
Trellises - everyone loves trellises. They make great patio covers against summer sun, and if you plant deciduous vines, you will still get sun in the spring. They make great walkways, especially as connections between spaces. A short trellis also makes a great frame for a gate.
Terraces/Rockeries - If you have a slope, the best way to keep it from eroding is to terrace it, or turn it into a rockery. There are also a variety of plants they hold the ground together very well, although some of them can be invasive. Terraces/Rockeries and plantings together will reliably stop erosion while still given a lot of options for visual interest. Terraces can turn a slope into more useful space by making it walkable.
Car Connection - make sure there is path from the car parking to the front door, or else the front door won't get used.
North face - people don't generally like to hang out in the shade, so either (1) make it something nice for the adjoining building to look at (2) make it a garden walk to pass thru (3) step the building down so that it minimizes the shadow area.