When you are out to eat, and are a guest, it is polite to take your cues from the host/ hostess. When you arrive at the table, allow the host to indicate where they would like you to sit. If they do not, then you are welcome to take a seat where you would like. It is also good etiquette to wait for the host/ hostess to ask you what you would like to drink, or eat, rather than just going ahead and ordering. When the food arrives, you should ALWAYS wait until EVERYONE has received their food before starting. When the host/ hostess starts at their food, then you can too.
Pushing other people out of the way to get your desired seat is NOT the way to go. DO NOT ever just order whenever you want; wait for the host/ hostess’ cue. Also, if the host/ hostess is paying for the meal, DO NOT order the most expensive thing on the menu. Ask around and see what other people may be ordering and stay in that same dollar range. DO NOT EVER just start eating as soon as you get your food. It is incredibly rude! Always take cues from your host/hostess.