If in the future you want to be in a certian coven, and you are mortal, do you have to be changed by someone from that coven?? I know it's probably a stupid question, but hey, what can I say?

I think so. I'm pretty sure that which kind of vampire you are is dictated by which coven turns you.

It more or less depends on which vampire in particular turns the mortal. An Ishak or Tarepha might be possessive enough of their fledgling to make them join their coven, while the Enashe and Nephim might allow said fledgling the freedom of choice between coven or independent. An Amman fledgling would likely remain with his/her parent vampire for some time, and then allowed the option of being turned loose.

And, as Nico said, the type of power that the turned mortal receives would probably be of the typical powers from their parent vampire's coven. That doesn't really restrain them from switching covens, however.

Okay, so I was half right. ^_^