The vast majority of religious leaders who claim to use divine power (clerics, priests, etc) effect their "tricks" via slight of hand, misdirection, or secret mechanisms. Many people believe that these are true acts of the gods. These things are seperate from the normal D&D magic because they often involve lengthy rituals and incantations, or a lot of hocus pocus but not much substance. True practitioners tend to use much more understated means. However, there are just enough true practitioners to lend credence to all the charlatans; the general public probably can't tell them apart. Where these true practioners draw their power from is another mystery...
People from more primitive and/or superstitious backgrounds might truly believe that they have powers: making a certain gesture drives away demons, saying a certain thing brings good luck. Mostly, these people do nothing that is particularly "magical." Occasionally, they might get (un)lucky, and something might have an effect. Again, a very few know what they're doing and have control of it.
Some folks experiment with alchemical substances and claim it is magic.
For the most part, people accept that magic is a nice fantasy: something that stage performers do to entertain on feastdays and nothing more. It may look real, but if you put your mind to it you can discover the trick.
Ostentatious yet understated displays of obvious magic like the one Malachi just put on where an observer can say, "There, that could not be a clever trick or a strange coincidence; that person just undeniably wielded magic," are truly unknown.
In other news, N'un T'Chauck will get 6 HP from his d12 HD + 2 HP from his Con for a total of 8 HP. Also, Jason is correct in his latest post, and Jdvn1 is essentially correct as well.
