With each date being only three (or five) minutes, what if after I meet somebody I'm still not sure whether to mark this person as "yes" or a "no"?

If you are undecided about whether to mark someone as a yes or a no on your matchcard, we would suggest that you mark them as a yes. This way, if there is a match (meaning they also picked you) you can take more time to get to know them later. And don't forget, not everyone has to be a love match. Some great friendships have also started at our events.
With each date being only three (or five) minutes, what if after I meet somebody I'm still not sure whether to mark this person as "yes" or a "no"?
I noticed that your web site said that if you do not have a match at one event you can go to another one for free. Is this true?
What should I wear to a speed dating event?
What is the procedure once everyone arrives at the Club/Restaurant?
Is anything provided at the speed dating event?
Is each person allowed to choose more than just one person to see again?
How long does it usually take to hear who you matched with?
Does everyone get an email match or no match?
How do I get the most out of the speed dating experience?
Do you have any speed dating tips for me?