after having wrote a text (toooo much complicated for my Japanese skills)in lang-8,, a Japanese wrote me this:
上手な文章で内容も良く分かる。
でも、日本人からすると文体が統一されていないので、頭がクラクラする。
全部の文章が「です」・「ます」で終わるのも、単調なので、体言止めなどの技術を考える時期に来ているんじゃないかな？

I'm happy for having found someone really critic.. but I don't get what the hell this 体言止め techique is... And I didn't get what 体言　means.

I'm not 100%, but I think it's saying like 青い空 instead of 空が青い or 光る星 instead of 星が光る

from http://members2.jcom.home.ne.jp...taigendome.html
○夕立の雲も止まらぬ夏の日のかたぶく山にひぐらしの声（新古今和歌集、式子内親王）

　「あの日」のヒグラシの声が、清冽に頭の中に響き渡りませんか？

Yeah, I think it's about describing the nouns before the nouns actually appear. Like, you could just say "The voice of the cicadas," but adding a bunch of stuff behind it makes it more...effective.

体言 refers to nouns and pronouns.

体言止め refers to ending a sentence with a noun/pronoun.

歓喜のうなりを上げるエンジン。
彼のくれた花束。
凛とした声を響かせる少女。

(from here: http://www.raitonoveru.jp/i/h/01d.html)

I think that's pretty bad advice. It's true that a text might become slightly stale if it ends with -masu and -desu every sentence, but you can use particles and stuff to spice it up. 体言止め is slowly becoming accepted and is nowadays used in magazines etc, but it's still in a sense technically incorrect and IMO shouldn't be used by beginners unless they know it's not going to sound odd.

Ending every sentence with です or ます is pretty bad style. There is a lot you can do to spice it up even if you don't resort to 体言止め. The most common method is to just make your sentences very long, reducing the number of です・ます you need to stick in per unit of text. Overcoming the "simple sentence barrier" is the biggest challenge in going from intermediate to advanced (for production).

For a (poor) approximation in English, imagine a post written like this:

I am Jarvik. I am from Canada. I study Japanese. I live in Nagoya. I am a translator.

vs

My name is Jarvik and I come from Canada. I study Japanese in my free time and currently live in Nagoya where I work as a translator.

The second sentence is almost twice as long, but it's a lot easier to digest (which is what the Japanese person complained about in his reply).

体言止め is a no-no in more formal writing, but in what amounts to a blog post it's perfectly acceptable. The person who replied to you just threw 体言止め out as an example (〜など) and didn't mean "YOU MUST DO 体言止め NOWWWWWW"

-edit-
Just checked out one of my JP friend's recent mixi posts. Of the two page post, only four sentences end in desu or masu (2 each).

Thank you very much, guys!
I got it now...
Anyway, I asked directly to him, and he replied:

Seechさん Wrote:体言止め：名詞や代名詞で文章を終了させること。

例）Francescoの文を体言止めにしてみました。
◯ 　そのために、世界遺産の最多保有国はイタリア。
◯　現在、イタリア中の劇場で働く人は法令に反対デモ中。
◯　今から情勢は悪化するばかり、
◯　もちろん独創的な人まだいるけど、有名になるために創造性は不必要。

My original text was:
◯そのために、世界遺産の最多保有国はイタリアです。
◯現在、イタリア中の劇場で働く人は法令に反対デモしてる。
◯今から情勢は悪化するばかりです。
◯もちろん独創的な人まだいるけど、有名になるために創造性は必要ないと思う。

So in short he's suggesting me to avoid the polite copula and to cut off the verbs when unnecessary... In order to improve the flow of the text

I think maybe he wasn't saying the です is bad to use, but the problem there is that you used 思う and してる, so perhaps he feels like using です on the other sentences creates a style conflict. If you want to make it all desu/masu form, this is my suggestion:

そのために、世界遺産の最多保有国はイタリアです。現在、イタリア中の劇場で働く人は法令に反対デモしてて、今から情勢は悪化するばかりです。もちろん独創的な人まだいるけど、有名になるために創造性は必要ないと思います。

I write my journals in the plain form and I occasionally have the same problem with だ (I don't know enough fancy words to use である). If I end up with two sentences in a row ending with だ I need to reword them. I try to avoid repeating words in both English and Japanese, but Japanese sentence endings are definitely a different kind of stylistic challenge.