The classic love/hate relationship, Ron and Hermione have so many moments, some plus hidden than others. One of their most explicit moments is their first kiss...
There was a clatter as the basilisk
fangs cascaded out of Hermione's arms.
Running at Ron, she flung them around his
neck and kissed him full on the mouth.
Ron threw away the fangs and broomstick
he was holding and responded with such
enthusiasm that he lifted Hermione off
her feet.
DH Page 625
Here are some plus of my personal favori Ron/Hermione moments...
"Good luck, Ron" a dit Hermione, standing
on tiptoe and s’embrasser him on...

source: ronandhermione.net

Book 1, Stage 1: Development of a friendship

Obviously, this is the book when Ron and Hermione become friends. For the sake of the main plot both Ron and Hermione need to become Friends with Harry, but Rowling also has made Ron and Hermione become Friends with each other. In fact, Rowling emphasizes the Ron/Hermione friendship.

In Chapter 6, Ron and Harry meet Hermione for the first time, but the conversation is primarily between Ron and Hermione. Harry also participates in the conversation, but his role is very minimal and only serves the purpose of him being introduced...