Many years ago, on the APD, someone mention that people in this
hobby go through different stages.
I went through a major collectoritis stage from 2002 till Sept '03.
I wanted to grow everything and anything. At one point, my 55g had
60 species and my 20g long had another 30 species. Furthermore, my
emmersed setup was overflowing with a dozen more! I was always eager
to try the newest plant on the block and didn't hesitate to spend $
getting plants in from Singapore and trading plants with people from
Sweden to Brazil. But enough was enough. I don't regret going through
this phase, since I got to observe how each species grows. When
time came to start sending away and chucking species, I knew which
ones would stay and which ones had to go. I had my 'palette' of 20 or
so species I really liked and could work from here.
As far as creating an artistic, aquascaping design, my way of doing it:
Take out all the plants. Empty the tank. Start from scratch.
Take out an ersable marker and measure the tank. Mark the four
focal points and lines radiating from it. VERY helpful.
Do you have your inspiration at hand? Sandy foreground? Hairgrass
with Japanese rock arrangement? Dutch tank with alternating stem
plants contrasting in color and leaf shape? You need a general idea on
where you're heading.
Take the wood and rock you are going to use and start positioning.
This takes me about an hour to get it just right.
Looks good? If you're going to add epiphytes such as moss, bolbitis,
or anubias, this is the time to do so. Carefully remove one
piece of rock or wood and tie down the plant. Place the branch/rock
back into the tank in its original position. To me, these plants are
basically part of the hardscaping.
Add the foreground plants next (if you have any, I opted for a white
sand foreground in my 55g and my cories love it).
Position the red/colored stem plants since these tend to draw and pull
the eye the most.
Add the green stem plants, positioning them with consideration to their
eventual size, growth rate, and leaf shape.
A couple days later, add the shrimp, snails, and algae eating fish.
A couple months later, adjust any wood or reposition plants. Take out
plants or add new ones, too. Nothing never comes out perfectly the first time around, especially when you don't know exactly how the tank will "grow in." At this point, add the fish you believe will complement the aquascape.
That's my way of doing it.

I have two tanks and they do not look
at all alike.
Carlos