I can recommend a couple of things to you. I'm not that experienced either, but I've been doing a lot of research. But don't take my opinion as though I'm very knowledgeable because I've a lot to learn.
A lot of things you don't believe in can't really hurt you. As long as you let negative energy roll off your shoulders, I think it's all good. Cleanse your mind and think positive :)
Just start with the basics first, read books or articles. Make sure they seem plausible, though! (Obviously if something is telling you you can become a mermaid or fly, then don't take it seriously.)
I would recommend using other peoples' spells first, but that's just me. As you get a feel for what spells are like then maybe you can try your own if you want :)
For beginners, you can try meditating and grounding yourself. This makes it easier to cast spells. I don't really know where would be a good place to start, maybe do exercises to sense auras? Get a feel for the energy flowing in and around you, and learn about visualization.
Magic is an energy that's subtle and works with nature, not against it.
As for being in a coven; I haven't been in one but they're usually groups of people learning from each other in different paths.
For that, it's your definition of witch. Some people can be raised pagan or Wiccan, by their parents. Others adopt these paths as they grow. So it goes either way. If you're wondering whether people are born with magical ability or not, I think everyone possesses magical ability to some extent.
I hope I helped answer your questions! Have fun on this site!