The Romans used concrete and stucco type finishes before the birth of Christ. Alex's example is the oldest and largest unreinforced concrete structure in the world. Concrete is in a plastic stage when mixed and placed. It has no flexibility once it begins to set and while they might not be apparent immediately, this is when they generally occur. With temperature change comes expansion and contraction and they become visible. Lower water to cement ratio of the mix and slowing the hydration of the mix as well as proper expansion and/or control joints reduce the chances of non-structural cracking.
Two mistakes that are common is trying to place too much concrete without adequate labor on hand. The finishers many times will have the mixer driver add too much water to the mix too allow him to work it later in the day which reduces the strength. Too much water will cause the cement to migrate to the top of the surface with the water and the finish will spall or slake off.
Another mistake is overworking the mix during finishing. Place, strike off (screed), float, and finish.
Proper curing in very warm weather might include a light mist of water to slow the hydration process.