It is hard for you to get a multiple-entry visa valid for 6 months because it is the first time for you to apply for China visa, but you can have a try, you need to bring the below documents to the embassy:
a) One completed visa application form with one photo (passport photo) attached.
b) A passport valid for more than six months with blank visa pages.
c) For people who goes to China for the first time: 3 months bank-statements and original air-flight tickets.
d) invitation letter from your friend, the copy of his passport and Chinse residence permit
There are single-entry (valid for 3 months) and double-entry tourist visas. Multiple-entry tourist visa can only be permitted by the Embassy on applicant's particular situation. A letter of explanation if requesting a multiple-entry tourist visa