When you come to the end of your speech resist the temptation to add something extra. Do not thank the audience and do not offer any apologies of any kind. Your prepared ending is your final statement. The ending is signalled by the way you make the final statement, by the tone of voice and the pace. To get it right you have to be intensely aware that this is the ending. You must say it as if you will never again speak to these people and you want above all else that they will remember these final words to their dying days.