Choose the particular aspect of your life that you wish to share with your audience. You should try to make this as unique as possible. Avoid generic topics like your favorite colors, sports team and astrological sign. Choose a situation or circumstance in your life that defines(or helped to define) you as a person. Perhaps why you fell in love with sculpting or what motivates you to climb mountains. These personal subjects define who you are.
Write the beginning of the speech with an attention-grabbing opening statement or paragraph. Presenting a peculiar piece of history that is little known to the audience that relates to your life will get the attention of the audience. A good example of an attention-grabbing opening line (if it were true) could be: My name is Alex, great-, great-, great-, great-grandson of Alexander the Great.
Fill the body of your speech with information relative to your topic only. Don't go off on a tangent that deviates from the main subject or aspect of your life that you want to share. A good way to do this is to outline the body of your speech and designate four or five main points that you want to emphasize. Some sample points could be: background information of why or what happened to make this particular aspect of your life important; how you began to pursue or become more involved with this part of your life; what happened along the way that makes this aspect significant; why you continue to do what you do or what good has come from this.
Conclude your speech by presenting the audience with a question that only you can answer. A good example for this technique would be: So where do I go from here? Answer the question by summarizing your speech and giving the reasons why the particular aspect of your life will continue to affect you.
Practice your speech in front of the mirror, and time yourself as you speak. Concentrate on eye contact and slowing your words down. Public speaking tends to make people speak faster, and, if you have a time quota, then you'll want to fit the speech perfectly into your allotted time. If you find that your speech is too short, add a few more details or elaborate to fill the void. Just remember to stay on topic--don't deviate from the scope of your personal speech.