Impromptu is not an even that gives much to the competitor.  A topic and a note card.  That is all Impromptu gives.  You supply the wits to best use the time being taken.  It is remarkable to witness a speaker create a speech in a snap with so little supplied by the event.  That's the wonder of the Impromptu Speaker.  They are cunning; using all they have and exploiting what is given.  Yet, with so little bestowed upon the speaker from the event itself, there are some who look down upon the note card.

Why?  Some view it as a crutch.  A tool not to be used by the experienced.  To a sect of Impromptu Speakers it is the mark of true ability to deliver a speech without the add of paper.  There is some truth behind this.  To be confident enough, and well versed enough, to speak without aid is rather incredible.  It is flashy too.  Impromptu showboating for sure!  However, not that all areas are like that.  Other Impromptu Speakers see the note card as an aid to make an already wonderful speaker better.  Whynottake advantage of a system that is challenging as is?

Whichever belief you follow, kudos on rocking Impromptu.  Though, if you do use a note card there are some ways to really use them and not let them use you:

Good outline.Know how to write an outline.  Whether using a traditional one with Roman numerals and letters, a bullet-list of points to hit, or a personal road map, be sure to know your system!  A crummy outline on a note card makes it useless while speaking.  What is my next point?  Where was that supposed to go?  That is a waste of time which makes you look unprofessional.

Write neatly.Spend your time talking, not deciphering cryptic text.

Glance.Most of your eye contact needs to be directed towards the audience.  Impromptu outlines are not meant to be held at eye level, your eyes pasted to your notes reading.  A quick glance to keep yourself on track is all that is necessary.

Holding.When not looking at your card keep it palmed in your hand, down by your side, in your non-gesturing hand. If the card is in your primary gesture hand then your audience will constantly be reminded of that sheet of paper.  You can gesture with that hand, just now it will be less obvious.  As Gandalf said, "keep it secret, keep it safe."  When you do need to glance, raise the card high enough to read comfortably but keep it out of your face.  The audience wants to see you not paper.

Continuous vocals.Do not pause between points just to read your card.  It creates a choppy Impromptu speech.  It also looks like you cannot think on your feet as well as the more fluid competitors.

Following these note card techniques can help improve your Impromptu Speaking skills.  This event is an art where polish is always required.  It can be the little details that push a speaker from one rank to another, and stealthily using a note card with all the precision of a ninja will get you noticed.  Note cards help guide and organize thoughts to avoid forgetting a major point.  Further, a note card's assistance could boost your confidence which is always great for a round.

Use one or not, it is your decision.  But if you do there is no reason why the card can't work for you.