Oh, believe me, I'm reading every word and sentence in this thread, and one other that I posted in the music production section. Sorry if I'm being rather ... quiet. I usually have a habit of doing that on a forum. I checked out the Songstuff Songwriting Articles section. All you guys were right - there is a wealth of information there that I literally spent hours reading on. So far, all of you have been particularly helpful to me, as you are posting your own unique thoughts on my questions.
Anyway, I read that RoadRunner Records website on the typical writing process for Dream Theater. I was actually surprised at how they do it; they usually jam and find ideas in their riffs and such. The way I thought it worked was when they had an idea in their heads, they would play it out and write it to paper. At least, that's how I try to do it. Perhaps the reason I become frustrated is because I might have this complex guitar or keyboard riff in my head, or I want to play a chord on the keyboard, and I immediately think that I should find how to play it, and formally write it out. Either that, or if I make up a riff on the guitar, and I try to write it out, I can't always get the form right.
I suppose that what I want to do in the future is develop an extremely large understanding of theory, so I will know how and why things sound they way they do, as stated by Lazz.
Once again, thank you. You all, so far, have been very helpful. Any other information would be appreciated, by the way.
Thanks,
-Mike