how to say no

Today Javier was the secretary and he did it very well. I liked very much the way, how he does his wiki. After that the teacher made a short presentation about assertivity and how we can be not too aggressive or not too passive during a conversation. The last part of the presentation was about, how we can say no in a polite way and we got an activity to this topic. After that we worked in pairs for 15 or 20 minutes and some of the groups performed their dialogues and we gave them suggestions, corrected their mistakes. In my opinion the pairs, who shared their dialogues with us, worked quite well and they just made a few mistakes. In the end of the lessen we were able to finish our activity.