When preparing the soil for a new plant it's a good idea to loosen up dirt and mix in 50% of a planters mix or mulch to add organic matter and nutrients to the soil. Dig the hole deeper and wider to help aerate the heavily compacted soil. Do not plant too deep, the soil level of the plant in the pot should line up even with the ground.
Making an earth berm around a shrub or tree will help the plant to retain water. You want this berm to extend to at least the diameter of the branches. This will help the water get to the root zone and not run off the ground to a different area.
Planting in the heat of the summer is more difficult and requires twice daily watering. Be sure that your irrigation systems are working before leaving town. 90% of plants that die in the summer are from lack of water.
Large trees, shrubs, and fruit trees have a higher success rate when planted between September and May. You can still be successful planting in the summer months, it will just take more care and water.