Question

how can I write a humerus speech for declamation on topic "I never reason, therefore, I am seldom wrong." ?
Writeacher
You mean "humorous"?

Read these very carefully. You should get some good ideas here:

http://mannerofspeaking.org/2009/11/29/anatomy-of-a-humorous-speech/

http://www.wikihow.com/Write-a-Funny-Speech