I should  study more   to be a better student and I would study more if I could find the time.

I could be   a  great scientist,  and if only the teachers would give me good grades in my classes,

I should be able to show all the world how brilliant I am.

  I should save the poor, and if I knew morality I would teach Morals to the wealthy,

and if I could persuade all the world to listen to me that I would tell everyone what they must do.

   Should anyone really listen to my ideas?  Of course not.  I have not established credibility, and I should first establish a great reputation and then  I could persuade all people to listen to my ideas.

http://www.italki.com/discussion/74241

For should :

http://www.englishclub.com/grammar/verbs-modal-should.htm

For would :

http://www.ecenglish.com/learnenglish/lessons/how-use-would

For could :

http://www.englishpage.com/modals/could.html

I hope I can help you

Ohh am glad, you are the only one who helped me. Thnk u so

much..