Know your soil.
Is it rocky? sandy? largely clay? Do you find pools of water a day after a heavy rain?
Is there lots of organic matter or practically none? Can you find earthworms in it?
What's the pH? What's the nutrient profile?
What have you been able to get grow in the past?
Know your sunlight.
Where's the structural shade?
Where's filtered light?
How many hours of sunlight does each portion of the landscape get?
Know your utility lines.
Where are your water, electrical, gas, and cable lines?
Know the governing rules if applicable.
Do you have an HOA that doesn't allow it?
For us, our soil drains well, is slightly alkaline, and has a modest amount of organic matter. I am able to find earthworms in it, and I have been able to grow a variety of plants. Despite some structural and natural shade, the light is very intense in all areas, and plants must be able to tolerate at least part sun and heat. In general, Texas natives, Mediterranean, and South African plants do best. There is a water and gas line running to the house from the street, and we don't have an HOA.