It is quite usual to drink cocktails before lunch and dinner in America and somewhat less usual, except in California, to drink wine with a meal. You can either have a cocktail in the bar, if there is one, while you wait for a table or for friends, or you can have one served before your dinner comes. At some restaurants the waiter/waitress will come to your table as soon as you sit down to ask if you want a cocktail, and you can then drink this while deciding what to order to eat. At others, there may be a separate cocktail waiter or waitress. In this case, you do not normally order wine from him or her but from the normal waiter- or the wine waiter is there is one.
Do not hesitate to order Californian wines. They can be excellent and in many parts of the country are cheap.
It is usual to have a salad with your meal, and a separate plate is provided for this purpose. The normal practice in America is to eat the salad before the main course. A wonderful American invention is the salad bar. In restaurants that have these salad bars the waiter does not bring your salad. You go to the salad bar and help yourself, usually to as much as you want. This is normally done after you have ordered your meal; you eat the salad while the main course is being cooked.