4) Know your location
Knowing your location is very important. Little things - what gate you enter, transport, parking, food, where the facilities are, where is the press room (if any), where you can setup, where you can locate yourself at the pitch. In many cases you are not briefed on where you can sit, but yet it is something you are expected to already know, as a professional.
So, where can you sit? Ideally you want to be positioned with the action coming at you. The end line is normally best for this, but where along there will really depend on the sport. You must also respect the other photographers and officials at any event. In many cases, it's first come, first served for pitchside positions. Make sure you are not blocking the view of the person there before you. In general, for field sports, the nearer the corner, the nearer the line you sit. The nearer the goal, the further back you sit, so that those out at the corner have a view right along the line. This is professional courtasy. You also have to make sure that you never block the TV cameras (if any).
It is also critical to ensure you are not blocking access - gateway, access route for medical services, access walkway for spectators and officials, and where players come on/off the pitch, etc.
In most cases, there will be areas you can and cannot sit. This will normally be told to you before the event, but it may not. Usually you cannot encroch on the team areas near the dugouts. 10M either side of this area is commonly restricted.
It will also be important to know where there is shelter for the really bad weather, just in case.