Personally, every time I set out to write a track, thinking "I'm going to write a track that sounds like <blah>!"... it never ends up soundling like <blah>. How I start a tune these days is just play around with samples, putting things down and trashing them again, until I hit something that sounds even remotely cool. Then I add a
little to it, if I think it sounds a little bland on it's own. At this point I set up my panning as well, so that essentially, this first pattern I put down,
I never have to touch it again.
After that's done, the most tedious part is done, which is actually starting the tune. Now it's just easy riding, intuition. After a few more patterns, I go back and do two things. I write a proper 'intro' set of patterns for the tune, and I go back and tweak the tempo. The reason I think the tempo tweaking is important, is because when I start a tune, my mind might be thinking at a different speed than the actual tempo of the song is. It's hard to explain, but what you're hearing in your mind isn't the same as the tempo it's actually playing at... sort of. So I fix the tempo until I think it's how I intended it to sound.
And then I just keep going and exploring until I run out of ideas, at which point I find a decent way to finish the tune. Last thing I do is fix volumes, dynamics, fix yet more panning, add more effects, fix transitions, and so on. The last little details that have to be fixed.
That's the way
I track, anyhow. At least that's the best I can summerize it. I don't expect anyone to agree with the way I do things, but hey, you asked.
Regarding what you said about structure. What I used to do alot is try to fill everything with a proper string section, bass drones, the whole kit and kaboodle. But eventually I found that it was just too much and it didn't help towards the sound... in fact, it bugged me after a while, and clashed with my ear. So now I figure that less is more, and I'm a strong advocate for minimalism. So my advice on that point is don't overdo it, and never second guess your intuition.
Don't worry about professionalism. Trying to achieve a 'professional' sound is putting yourself in a box, limiting your creativity. Don't.
This post is too long. My apologies.