What address to put on L visa?

If you will stay with your friend in his/her home, an invitation letter is required as well as his/her Chinese ID, the invitaion letter should include detailed contact information as well as the address. If you will mainly visit Shanghai, an address in Shanghai is better, otherwise, you have to show hotel booking.

What if I'm landing in Shanghai, but not staying in Shanghai? I think we will be traveling the same day. My friend's home is in Dalian... unfortunately, it's 18 hours from Shanghai. Would that not fly on the application?

What kind of information should be in the invitation letter? Her passport number, full address, telephone number, date of my travel-- what else? Does she need to include my personal info (date of birth, passport number) in the letter as well, or is that not necessary? I just want to be completely sure of what needs to be on the application because I'm making a 5 hour trip to the nearest consulate..

Actually, here's another thought. If I need to put a Shanghai address down... I have a cousin that lives there. Can I put his address down, but still list my friend as the inviter and the address at which I will be staying the rest of the time?

Hi, the invitation letter should include the following items:
(1) Personal information of the applicant, such as name, gender,and date of birth.
(2) Purpose of the visit, travel itinerary such as date of entry and exit, places of visit, relationship between the inviter and the applicant, and who will bear the expenses of the applicant.
(3) If the applicant is invited by an individual, please provide copies of inviter's ID Card if Chinese; passport information page, valid visa or residence permit for foreigners.
In your case, invitation letter from your friend is ok, you can put her address in Dalian to the application form because you will not live in Shanghai after arrival.