It is essential that posts of any kind are plumb. For projects such as decks or fences, make sure the hole is vertical rather than at an angle and the bottom of the hole is level. The hole needs to be deep enough to support the structural needs of the project as well as meet code requirements. Use the proper concrete mix, gravel or other fill material for the hole. Allow the concrete sufficient time to cure before proceeding to the next step.
Digging out the footing area for a patio, concrete pad or retaining wall requires tamping and leveling for a solid foundation. Excavations for ponds, especially those lined with flexible sheet liners, must be smooth and free of jagged projections.
Other underground obstructions that you need to locate or consider include septic fields and tree roots. Look up above also. Before you plant trees under overhead utilities, make sure the plant you have chosen will not interfere with the poles or cable. Before you dig for fences or privacy hedges, check property lines and easements.
Granted, digging a hole is usually not a lot of fun, especially if you've got a lot of them to do. It helps if you have the right tools. Shovels, spades and forks are the most common implements. For bigger jobs, a digging bar, post hole digger, mattock or pick may be necessary. Power tools such as tillers and augers can actually make digging fun. Use the right tool for the job so that the tool itself can do most of the work. Pace yourself properly to avoid overexertion and sore muscles the next day.
Caliche is a concrete-like soil deposit that occurs in the Southwest. These layered deposits of calcium carbonate restrict roots, increase soil salinity, and reduce the plant's ability to take up iron (an essential nutrient). If your soil contains caliche, dig a slightly wider planting hole. Remove the caliche and add a quality planting mix to the hole. If caliche prevents digging a hole as deep as the root ball, opt for a smaller plant. Make sure the roots are covered with soil, they should find a foothold as the plant matures.