b2 visa through H1B sponsorship or OPT visa?


I am in US for last 2 years as a student, but just started my OPT 1 month back. My elder brother is in US for last 7 years and is on H1b but filing for greencard. I have my graduation ceremony in may and wanted my parents to come to US. I have already applied visa for my parents and me when i was in india in 2010 but all of our visas got rejected. Then my mother applied again and she got rejected this time too. Now we want to apply for our parents tourist visa and want to know what steps should we take care of. Both my parents are in government job mother is still working but father is retired. Please ask me if anybody needs more information from me.

Thank you.