@Baka_Neko:
Everyday, my Japanese class would start like this:
Teacher: Hai, hajimemashou! person-san.
Person (person in charge of duties that day): Kiritsu! Rei!
Class: bow Konnichi ha
Person: Chaku seki!
Teacher: roll call
End of class:
Teacher: Hai, person-san.
Person: Kiritsu. Rei.
Class: bow Sayounara.
We did that in my high school Japanese class.
Person: Kiritsu, kiotsuke, rei. bow
Teacher: Mina-san, Kon'nichiha! bow
Class: name-sensei, kon'nichiha! bow
Person: Chakuseki.
At the end of class:
Person: Kiritsu, kiotsuke, rei. bow
Class: Jaa mata ashita. bow… or scramble to get things and leave XD
In college... it's like nobody says hi. A few random "kon'nichiha" scattered around. Sometimes I feel like being late to class just to bust in and declare "osokunatte sumimasen!" to get that Japanese class feel XD.
@Baka_Neko:
It doesn't have to follow the family name. A lot of the Japanese people I've talked to have said "firstname-san". Ok….name name name....Sanabe Yoriko. You can call her "Sanabe san" or "Yoriko san". Just go with what other people call her. If you are her class mate, you will probably call her "Sanabe san" (her last name). If you are her friend, you might call her "Yori chan", or even "Yoriko". If you are her mother/father, you might call her "Yocchan!". There are other ways too. To be super cute (cho kawaii) you could say "Yori tan~!" or something. There are so many different ways to address people, but "san" is the safest. If you aren't sure, just use "lastname san". 
Oh, right right. I forgot about it used with first names…
Eee... I'm such a nerd. I find these conversations fun.