Bismarck.Dreadnot said:
»-kun is male of a younger age then you, or someone of a lesser position. -san is for an elder(Mr. Ms. ect.) -chan is for female, or something cutesy. -sama is someone of a higher position or power.
Don't forget Senpai, Kohai and I think there's one other I'm missing for higher positions than yourself.
edit: Mainly find that important because the way I learned it sama is an extremely respectful term that is somewhat awkward to use when talking to EVERYONE higher than you on the pyramid. :x