I'm doing this stuff for my college chemistry class. Hope I can help...
First, let me tell you the relationships
a. Relationship between [H+] and [OH-]
Kw = [H3O+][OH-] = 1.0 x 10^-14 (mol/L^2)
Now, if like me, that confusion totally messed with your head, here's my dummie way of remembering...