If, after looking over the menu, there are items you are uncertain about, ask your server any questions you may have. Answering your questions is part of the server's job. It is better to find out before you order that a dish is prepared with something you do not like or are allergic to than to spend the entire meal picking tentatively at your food.
An employer will generally suggest that your order be taken first; his or her order will be taken last. Sometimes, however, the server will decide how the ordering will proceed. Often, women's orders are taken before men's.
As a guest, you should not order one of the most expensive items on the menu or more than two courses unless your host indicates that it is all right. If the host says, "I'm going to try this delicious sounding cheesecake; why don't you try dessert too," or "The prime rib is the specialty here; I think you'd enjoy it," then it is all right to order that item if you would like.