hey guys,please tell me a little about TA,GA and RA's of universities in us.
i am interested in applying to aid my college funding,
it would really help if i understand the basic criteria that they look for.

I just got admitted into third year mechanical engineering in SPCE and my cpi is 8.0
i am looking forward to go during fall 2015
how much should i score in GRE and toefl to assure an assistantship?