1 drink for each appearance of the following people:
Gosunkugi
Mikado
Azusa
Tsubasa
Konatsu
Akari
Herb
Ranko Tendo (*NOT* Ranma-chan)

The Jyusenkyo Guide
Nodoka (2 if she doesn't find out Ranma's secret, 3 if she insists he 
commit seppuku when she finds out)

How about Sentaro and Satsuke?

Do you mean Sasuke, the Kunou's ninja in the anime, or Satsuki, Sentarou's
wife?

3 drinks if any of the above are major parts of the story

2 drinks for each appearance of the following people:
Amano Akemi
Juyza
Kaneda Saotome
Buford
Charlotte
Victor
Sunshine
Cosmo
Shampoo's mother or father 
Any new Amazons

Does this include alien amazons?

Oh, dear... that sounds bad.

Kun-chan...