There are exceptions of course, but at a beginners level it might be best to start off thinking of "nan" when used with desu, da or with compounds (nannin, nannichi etc) and "nani" as coming before particles such as wo, ga, mo or ka.
Originally posted by Arashi Before any "t" sound (nante yomundesu ka?); "d" sounds are just modified "t" sounds, so they count too."ji" (as in, ima wa nanji?).
This is so confusing, I wish I just automatically knew the language, but only a wish.*sigh* Maybe when I go to college I'll learn it since my crappy high school doesn't offer it.