Make the advertisement a little bit scientific like..
hamara sabun hathon se 4,00,00,00 Bacteria ko jaan se mar sakta hai rather than our soap is the best
Make it a little bit filmy by introducing actors like madhuri dixit or katrina and in the end be like zara sa (whatevr your saop brand is)jus like zara sa lux lol:p
its cliche but it works!!
And make a funny joke here and there to keep the audience absorped
always make funny hand gestures to attract the audience
And at the end ..go to the teacher and declare that your teacher is so beutifull jus because she used your soap
declare that yr soap contaisn glycerine (it actually removes pimples ,i tried some real gylcerine on my face,lol stole it from chemistry lab while doing stomata experiment):p