Aside from being able to think of an Impromptu speech in minutes and channel Robin Williams for eloquent, uninterrupted words, as a speaker of this event you must also understand how to manage your time. For the nitty-gritty read further.
The very first thing that your Impromptu brain must grasp is how to train yourself to almost subliminally be conscious of time. While presenting your speech you should focus on your structure, words, and delivery. Giving a great speech is a must. However, while those processes are consciously occurring there needs to be a part of your brain tuned into the time signals your judge is giving. In Impromptu, timing literallyiseverything, and part of your rank is based on how you use your minutes. Be aware.
Secondly, knowing the general structure of time management is crucial if you wish to use your time to your advantage. Most leagues have their own, special-as-snowflakes rules for Impromptu. Either ask your coach for details or look them up yourself on your leagues website. For the purpose of this article a standard structure of a ten minute limit will be followed (which does seem to be the average time allowed). Now, in most leagues once you receive a topic you have prep and then speaking time all within your ten minutes. Therefore, when allocating time the basic premise would be to allow a maximum of five minutes for prep and five minutes to speak. This breaks your speech down into one minute breaks. One for the intro, one for each body (a total of three), and one for the conclusion.
However, it must be said that most Impromptu judges reward those who use less prep time and utilize the majority of their minutes for speaking. This could mean spending 3-4 minutes in prep and then 7-6 in speaking, respectively. It also is rewarded when distribution of time is equal when delivering your speech. This means if you are using five minutes to deliver a speech than all body paragraphs should be one minute in length. Equal dispersion displays a conscious effort to be in control of time management and helps with a well-rounded speech.
Thirdly, knowing hand signals and at what point in your Impromptu you should see them will keep you from going over time. During prep many judges vocally give 30 second and minute warnings. Once you begin speaking they should signal non-verbally. Five fingers for five minutes (and so on for four, three, two, and one). A closed fist means thirty seconds remain. You may see a five second count down with fingers. If you go over and extend past your grace period a judge will signal for you to wrap it up. This usually is a pointed finger upward going around in a circle, like a moon orbiting a non-existent planet.
So what signals should go where roughly? Assuming you cut your prep time down to 3 minutes, it would go as follows:
PREP: vocal signals through 3 minutes
Introduction: 1:00 (6 minute signal)
First Main Point: 1:30 (5 minute signal)
Second Main Point: 1:30 (4-3 minute signal)
Third Main Point: 1:30 (2 minute signal)
Conclusion: 1:00 (1 minute; 30 second signal)
These represent ideal conditions under a fast prep time. You may require four minutes to prepare. If four is more accurate for your style than you should be aiming for a little over one minute per point/intro/conclusion, thus you can look for a more standard countdown. In the above scenario, if followed to these maxed out time limits, prep and speech would take nine minutes and thirty seconds, thus giving some wiggle room if needed.
Finally, practice is the only method to improve Impromptu time management. Doing is how to become skilled. Through practice you will learn how to speak under pressure, which is challenging and can cost you time until you develop flow. Further, practice will allow for you to compensate for a blunder or other factors of "wasted" time, such as the seconds it takes to walk from your desk to the front of the room.
Impromptu time management is not as simplistic as one would think. Learning it is difficult. It takes effort and work. Mastering flow is not something that can be picked-up by most after a tournament or two. It is a skill that is nurtured and constantly improved upon. Do not feel ashamed for beginning at the 50-50 division of prep and speaking time. Most Impromptu speakers do. Practice, train hard, and your flow and time management will blossom into Impromptu gold.