How do you decide where to plant trees and bushes?

Figure out how large the trees/bushes will grow. The do need full sun. Plan the garden layout on graph paper first. That's what the pro's do.

https://www.starkbros.com/growing-guide/article/fruit-tree-care-planning-planting

Research the specific trees. You can find out how tall they will grow. It depends on the property size. I have had apple, peach, and cherry trees that are a smaller variety and they grew 15 to 20 feet tall. The root systems usually grow at least as large as the top so don't plant too close to sewer lines or foundation or walkways due to falling fruit. I have used everbearing strawberries as foundation planting *this depends on your climate. Good luck

Don't grow close to house as roots will go under house. Go to middle of yard

Never too close to a structure. Common mistake. Not only for roots but when they are mature. Fruit trees together. Like an orchard. They need cross pollination from bees. Try having some balance to it. Bush on one side and bush on other but don’t do it all too matchy or in a straight line. You want curved beds. Use garden hoses to help map some ideas before digging in with a spade. Consider color you get from planting’s and different times of the year. Also sun/shade.

I would go by how much sun they require and keep an eye on where the sun is at in your yard. You dont want it to get to much or to little. Depending on the type.

The easiest way to do this is to drive around an already established neighborhood that has trees and bushes that are at least 15 years old. See how many properties have a look or a plant that you like. Take photos and then knock on the door. The person inside might be thrilled to show you around. As Sal said, make a sketch of your property and what you would like to plant. Note on the drawing where the sun rises and sets and the existing shade from already growing plants and/or buildings. Then, take the photos and drawing to a garden center and buy the plants you want. Work on one section of your property at a time. If you have time, buy smaller plants and save a lot of money. If you are in a hurry, buy larger plants. As jbunner noted, make sure to measure distances from your house, septic systems, wells, and other plants and note exposures, views, etc. If you want large trees, be aware of underground cables (call before you dig) and the shade and/or wind block the tree will provide. Trees and bushes have different looks in the fall, winter, spring and summer. Many plants shed flowers and seeds and leaves that will require future clean up work. Enjoy the process and admire your efforts often! I never get tired in the spring of looking out at my blooming Japanese cherry tree (now over 35 feet tall and planted 24 years ago) as I sit at my dining room table.