First, get in touch with all those who will be included in the adventure, or if all are not available, at least talk to the better players so that you will be able to set an objective for the adventure. Whether the purpose is so simple as to discover a flight of stairs to the next lowest unexplored level or so difficult as to find and destroy an altar to an alien god, some firm objective should be established and then adhered to as strongly as possible. Note, however, that inflexibility or foolish stubbornness is often fatal. ...
Co-operation amongst party members is a major key to success, particularly when the characters are relatively low-level. Later, when players have characters of 9th, 10th, or even higher level it will be a slightly different matter, for then some adventures will be with but one or two player characters participating, and the balance of the group will be made up of henchmen whose general co-operation is relatively assured. But to gain the upper levels, it is essential that a character survive, and survival at lower levels is usually dependent upon group action and team spirit. Co-operation must begin when the party prepares for the adventure and continue through safe return to base and division of spoils -- including the special treatment required for any unfortunate characters cursed, diseased, maimed, or killed. ...
When everything is all set, it will take only a very few minutes to organize the group for the adventure once time for actual play begins. Your referee will certainly appreciate this, for his or her enjoyment comes from adventuring, not from waiting for a party to get their act together. ...