Because trees are often the larger elements in a landscape, when designing a landscape one of the first things I consider is placement of shade and ornamental trees.
Shade Tree Placement
Shade trees around a home do more than just create a structure and give strength to the landscape. They can also be effective energy conservers. For this reason, and because they are more difficult to relocate when established, their positions in the landscape should be chosen carefully.
Shade trees, such as oaks, maples, and elms are best planted far away enough from the home that their limbs will not eventually grow on top of the roof or cause damage if they break off in a severe storm. We never know what Mother Nature is going to throw at us so it's better to be safe than sorry. A good rule of thumb is to plant a shade tree at least 20 feet from the house. Also, before planting, the proposed location of shade, flowering and other ornamental trees should be considered both from inside the home and from several angles outside in the landscape as well.
Deciduous shade trees (those which lose their leaves during the cool season) planted 20 feet from the house on the south or west sides of the home will shade the house during summer, lowering the indoor temperature from 8 to 20 degrees F. In the winter, when the trees leaves have fallen, sunlight is allowed to strike the home helping to reduce heating bills.
Trees should be planted far enough apart to allow summer breezes to blow through them. Space the trunks so that the branches will not quite touch when the trees are mature. You'll need to do a little research on the type of tree to know their average width at maturity.
Shade trees are usually best located to the sides of a home, where they will frame the home rather than block it. That being said, if the front or back of your home faces south or west, you can locate them so that they do not entirely cut off the view of the home. Never plant a shade tree where its trunk will block the view of a front door, a beautiful window, or some other attractive feature. Doing so can make the house seem less significant and stops your eye from traveling to the most outstanding features of the home. When placed right, trees can make a home appear longer or larger than it is and should lead your eye to the front door.
Flowering Trees 
Usually smaller than most shade trees, flowering trees, such as flowering cherries, chaste tree, flowering crabapple, crape myrtles, dogwood, redbud, and purple leaf plum, demand a location that draws attention to the best of their attributes. Flowering trees can be planted singly as an accent, in a group to create a weighty mass, or repeated in a row to create a straight or a curving line. A flowering tree shows itself off well in almost any area of the landscape, but is most effective with a simple background that plays up the flowers and silhouettes the outlines of the branches. This could be a fence or shrubs planted in the background.
Ornamental Trees
Smaller growing ornamental trees, such as many varieties of holly and hybrid Japanese maple, which can add tremendous aesthetic as well as monetary value to a property, can be planted singly to accent and draw attention to specific areas or features in the landscape. They can also be planted in small groupings or in a straight or curved row.
Some trees, such as weeping willow, river birch, and other moisture-loving trees are perfect for use around bodies of water such as lakes, ponds and streams. Keep in mind that these trees have roots that can extend 20 or more feet from beyond the perimeter of the branch system. Be careful planting these types of trees too closely to swimming pools and other contained man-made bodies of water as their root systems can often break through barriers that contain water. Also keep them sufficiently spaced from underground septic systems and lines.
Evergreen Trees 
Tall growing evergreen trees, such as arborvitae, cedars, cryptomeria, cypress, holly, junipers, magnolias and others can be planted in a straight or curved line to provide a screen or buffer to block unsightly views, wind and/or noise. They can also be useful to frame in the corners of homes and other buildings and structures. When planting evergreen trees in a row, be careful to space them sufficiently according to their width at maturity. You want to space them so that when mature the branches of the trees will barely touch. This allows for good air circulation and lessens competiton among the roots. If there is sufficient space in the planting area, plant evergreen trees in a staggered rather than straight row. Doing so helps to create a better visual barrier. For example, if a specific variety of evergreen tree grows 10 feet wide space the front row 10 to 12 feet apart. Then set your second row 10 feet back and stagger these between the plants on the front row. Now you have created a better visual barrier!
Hope these tips were helpful!
