I've got to admit, something I've learned from people such as John is to try and read recently published authors who may be writing similar to your own aims. I think it helps immensely, because not only does it provide suggestions on style and construction issues, you can also see if your "great ideas" have already been done and killed. And also you can use places such as forums to get feedback as to which character formats are fan favourites.
2c.
That's very good advice.
Personally, I'm finding I didn't really make too many style and construction errors, but that was mainly because I spent the first couple of years planning the series and the background to my world beforehand. During this time I'd also read a few books on composing sentences, grammar, and other things like that; and I'd also bought a few books on how to improve my storytelling. In short, I did everything I could to ensure I wouldn't fall into one of the many pitfalls that most new writers do. The only thing I didn't get to do was to read lots of "normal" books as well. As said, I know I should have (since that in itself is a pitfall), but, suffice as to say, since I don't want to go into details, I had a choice between wrting (which involved all the things I mentioned) or reading: I chose what I love best, writing. But I'm reading loads now! I just hope it's not too late...
As for ideas on character favourites, I've already got enough people in my story -- and they're all unique (hopefully). I spent a long while thinking up the correct personality for each, and, in fact, someone complimented me over how well I'd portrayed them. In my opinion a character fits the story; for me, I can't just say "Ah, people love that type of character, I'll have one of those in it". My writing just doesn't work that way...
But, I agree, this forum is definitely the place to chat, swap ideas, help other writers and such. I love it here! The only problem is the longer I'm here, the less time I'm spending on my writing. That's the problem: this forum's too addictive!
So thank you, Brian and John, this is a wonderful place for advice.