Solar sites and books say south. Can it face east or west? Are there times when an orientation other than south is better? The answer is yes. Your solar contractor should be able to discuss with you how they want to orient the array a specific direction and why. Often times a few degrees East of south will be better if there is heavy shading on the West for example.
You may take this for granted and not want to get involved in system design issues, but you should ask the contractor to oversize each run. It is a very inexpensive option and can improve overall system performance. If you have several inverters, it is imperative. Multi-inverter systems act differently than single inverters. They need a significantly larger wire size to control voltage.
This is difficult unless you do your homework. The first thing you must do is to choose a reputable contractor who knows what they are doing and has the experience to back it up.