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. You can dig the hole a little deeper and wider to help aerate the heaily compacted ground. However, be careful to not plant too deep. The soil level of the plant in the pot should match the soil level of the plant once it is in the ground. Planting too deep can lead to trunk rot and other complications.
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 rarely a good idea. Seasonal plants, such as summer vegetables, will take the heat with stride, but trees and shrubs are likely to become stressed from not receiving enough water, leaving them vulnerable to seasonal pests and disease. The best time to plant most trees and shrubs is the fall or spring. Your plants will be able to maintain moisture better and will be more prepared for the scorching, summer heat.
Fruit trees, however, should always be planted in the fall while they are dormant. If planted during their growing season there is the possibility that they will become shocked and die. While that is the severest outcome, your fruit tree will be unnecessarily stressed, which can affect produce production and leave your tree susceptible to pests and disease.