Culture-oriented Common Days>Communication-gaps>
Distinction between "wa", "ga" and "mo"

"は(wa)" is used to assign the subject of a sentence following it in most usual cases(whose purpose is to specify the predicate), especially in cases subject has other candidate(s) and predicate varies in relation to the subject's selections.
It is also used to exclude certain candidate from subjects.
English Japanese
Official languages in Canada are English and French. カナダの公用語は英語とフランス語だ。
（英語とフランス語がカナダの公用語だ。）
Hope after retirement is a scarce pension. 老後の支えは僅かな年金だ。
（僅かな年金が老後の支えだ。）
He committed a serious crime. 彼は重罪を犯した。
For me, coffee. 僕はコーヒー。
He rather is a commedian. 彼はむしろコメディアンです。
Partner is helpful on a journey, and sympathy is important on the life. 旅は道連れ、世は情け。
I suspect that although most of them are innocent, she at least must be guilty. 私は大半の人は無実だが、彼女だけは有罪だと思う。
It is not always so. そうとは限らない。

"が(ga)" is used in simple sentences following the subject to specify subject itself than the predicate.
English Japanese
It's me who will be the representative of the miss-contest. 私がミスコンの代表になるのよ。
It's me who ordered cappuccino. 私がカプチーノを頼みました。
Not she but he must be the principal offender if so. そういうことなら彼女でなく彼が主犯でしょう。
The last chance is now. 今が最後のチャンスだ。
I'd like a girl for it. Not a boy. 女の子が良い。男の子は困る。
Most of them are no good, although this piece only is acceptable. ほとんどがダメだ。この品物だけは良いが。
I only love this piece among his works, for all I don't care for others. 私は、彼の作品はほぼどうでも良いが、この作品だけが好きだ。

"が(ga)" is used in compound sentences especially in the condition-defining part following the inner-subject of that part. It is also used in a result-defining part that has rather unexpected selection on the inner-subject.
English Japanese
I am sad if it is true. それが事実なら私は辛い。
I will live strong even if it is true. それが事実でも私は強く生きる。
If it rains tomorrow, please stay by me. もしも明日が雨ならば、傍に居て。
If it is a cat, I will progress, and, if it is a tiger, I will flee. それがネコなら私は進み、それがトラなら私は逃げる。
If it is a cat, I will progress, and, even if it is a tiger, I won't flee. それがネコなら私は進むが、それがトラでも私は逃げない。
If wind blows, leaves scatter. 風が吹けば、木の葉は散る。
If wind blows, tab-shops gain profits. 風が吹けば、桶屋が儲かる。(A famous example of an absurd causality.)

"が(ga)" is used in the clauses following the inner-subject of the clause as following.
"の(no)" can replace it if the clause is used as the modifier of a noun.
case English Japanese
the clause is the
modifier of the subject		 Those who lie a lot are not relied on. 嘘が多い人は信用されない。
（嘘の多い人は信用されない。）
Those with brown feather are female.
→ Ducks whose feather is brown are female.		 羽が茶色いカモはメスだ。
→ 羽が茶色いのはメスだ。
（羽の茶色いのはメスだ。）
It is after a long while that she sings on the stage.
→ An occasion that she sings on the stage is after a long while.		 彼女が舞台で歌うことは久しぶりだ。
→ 彼女が舞台で歌うのは久しぶりだ。
（彼女の舞台で歌うのは久しぶりだ。）
the clause is the
modifier of an object		 Audience waits me sing on the stage.
→ Audience waits the moment when I sing on the stage.		 聴衆は私がステージで歌うことを待っている。
→ 聴衆は私がステージで歌うのを待っている。
（聴衆は私のステージで歌うのを待っている。）
the clause is
predicate		 Elephant has a long nose.
→ Elephant is an animal whose nose is long.		 象なむ鼻ぞ長き獣。
→ 象は鼻が長い。
I dislike that actress. 私はあの女優が嫌いだ。
I lost a favor on him. 彼には愛想が尽きた。
the clause is the
complement		 I suspect that she is the criminal. 私は彼女が犯人だと思う。

"も(mo)" is used in the sentences that leads to the same or alike result(like "too") for more or equal two matters or a wide range of selections (I learned in school that there are two different kinds: "identical-mo" and "astonishing-mo". But thus, it is consolidated in a unique category).
English Japanese
Men are said to be no exception to write a diary. 男も日記を書くらしい。
Women would do it also. 女もするのだ。
So, you fairly like it! あんたも好きねえ。(As a simple logic, "は" should rather be used here. However, device to obscure the teller's opinion on what the world's majority is is some tenderness and taste of such a saying. Or, the teller may be deploring the world's recent tendency.)
Anything is useless, whatever you do. 何をしても無駄だ。
For me too, coffee. 私もコーヒー。
No one is to blame. 誰のせいでもない。
Even storm is not fearful. 嵐も怖くない。
Storm blows, and, rain falls. 嵐も吹けば、雨も降る。