See the wikipedia article on Japanese honorifics to get the basics of honorfics. The below is an incomplete accounting of honorific usage in the Ranma ½ manga.
Ranma is generally disrespectful and rarely uses any honorifics. Though he will occasionally use them and does know the proper usage. He refers to Kuno with -sempai, sarcastically often though. Calls Soun ojisan (uncle), Ucchan (childhood nickname) for Ukyo, -san for Kasumi (though also has used oniichan), Ojiisan (grandfather) for Happosai and Obaasan (grandmother) for Cologne occasionally. For his mother uses ofukuro in his thoughts and obasama when he spoke to her while pretending to be Ranko. While in disguise he uses the appropriate honorifics for the situation; example during the time he pretended to be a normal girl to get in the locker room where he thought a magic pool was under (it had already dried out) he used -chan for Akane. He also uses insult names sometimes like calling Nabiki Bitch (in fan translated - the actual Japanese word is different but basically means the same thing -temee which is actually a rude form of you) or Old Ghoul to Cologne.
Cologne uses -dono when referring to Ranma which implies that she respects Ranma to a large degree.
Kuno sometimes uses -kun for Akane.
Soun and Genma use family name-kun when talking to each other, i.e. Tendo-kun.
Genma has used -kun for Akane.
Akane doesn't use any honorific for Ranma and if she starts to do so it would imply that the relationship is breaking apart. She refers to Ryoga as Ryoga-kun and Kuno with -sempai. Uses ojisama for Genma.
Kodachi uses -sama for Ranma, and family name-san for everyone else, she is extremely formal.
Konatsu uses -sama for Ukyou, Ranma, and Akane. He praises and raises status of other people while lowering his own status.
Nabiki refers to Kuno with -chan probably to annoy him and calls Ranma by his family name most of the time. Ojisan for Genma
Happosai uses -chan for Ranma and Akane.
Ryoga is very respectful to most people and refers to them with -san. He even uses that for Akane, even poked it into the rock while writing her name in the breaking point arc.
Shampoo doesn't use honorifics because she either doesn't know the proper usage or is purposely being rude. Calls Ranma Airen which is in Chinese the dominant word used for spouse (literally means love person Ai=love Ren=Person) .
Ukyou normally uses -chan when referring to anyone and Ranchan for Ranma.
Hinako uses the family name-san for Ranma and the other students.
Principal Kuno uses English honorifics. For example, Miss Akane.