*yoda's voice*
Patient, you must be.
A lot of trials, you'll have to do.
One day, will be in your tank, a piece of nature.
I usually build a tank before I... got the tank. It begins with a driftwood or a rock that inspire me. For this one, I bought first the driftwood on the right. It was so beautiful, I instantly wanted to make something with it ! Then I built the aquascape from it, placing another driftwood, then some plate rocks and so on.
In another tank, a nano I made 3 weeks ago, it started with some volcanic rocks I found this summer, during holidays when I was walking though a mountain with some friends of mine. When I saw them, I said to myself : wow ! Gonna make a 20 L with these ones !!! (can't help myself collecting stones since I was kid... my parents was about to euthanize me cause of the usual 20kgs of stones I've been brought back home every holidays). And I made it one month after during a sunday afternoon.
I never draw a plan on a paper / screen. Indeed, I start to built the tank in my mind. I let it grows, give it time to make it mature. Then, when I feel it's ok (=nothing to remove), I built it somewhat quickly.
You have to train yourself to know instinctively what kind of plants / driftwood / stones you can use, how you can match them.
[edit for some mistakes I just saw]