「① First come, first served」が[優先順位](https://eikaiwa.dmm.com/uknow/questions/40712/)に従って対応することを意味します。
「comes」では無くて、「come」です。
[チケット](https://eikaiwa.dmm.com/uknow/questions/39775/)の場合、以下の様な例があります：
Tickets are available on a first come, first served basis（チケットは先着順位で承ります）。
ジュリアン
First come, first served; 先着順を表します。
例：
We serve our customers on a first-come, first-served basis.
先着順でお客様の[対応](https://eikaiwa.dmm.com/uknow/questions/36228/)をしております。
関連
[申し訳ございませんが](https://eikaiwa.dmm.com/uknow/questions/62406/)、ご予約は承っておりません。
I am sorry but we don't accept any reservation.
当店ではご予約は出来かねます。先着順となっております。
There is no reservation available in our restaurant, whoever comes first will be served first.
3. Please stand in line and come forward one at a time.
1. This is an idiom appropriate for this situation.
2. This is an instruction to a group of people about the required process of being attended to.
3. Another instruction for a group of people. The first in line gets to pick/or is attended to first.
"First come, first served." - is an expression used to tell someone that the first person to arrive someplace will be tended to first. For example, if you go to a restaurant and are the first one at the table to get there then you may be the one to order first. Or, if you are standing in line and you are first then you will be the first one to be waited on.
"First come, first served."（先着順）- ある場所に最初に来た人が最初に対応されることを表す表現です。例えばレストランで、最初にテーブルについた人が最初に注文を取ってもらえる。又は列に並んでいて、列の最初にいる人が最初に接客してもらえる、ということです。
"You snooze,you lose."
A casual way of saying that of you are not quick enough you won't get to pick first.
snooze = to sleep
"A first come,first served basis."
Whoever is there first will get to choose first.
"You need to following a queuing system"
This means that you will be served according to your position in the waiting line.
"You snooze,you lose."
A casual way of saying that of you are not quick enough you won't get to pick first.
snooze = to sleep
「Snooze（居眠り）すると、Lose（損する）。」
急がないと、先に選べなくなる、という意味。Snoozeは、寝る、と言う意味です。
"A first come,first served basis."
Whoever is there first will get to choose first.
「先着順。」
先に来た人が、先に選ぶ権利があること。
"You need to following a queuing system"
This means that you will be served according to your position in the waiting line.
「列に並ぶシステムに従わなければならない。」
列に並んだ順に、サービスを受けられるということ。
You can use the above sentences to respond to someone that maybe wondering how the system works or why someone is picking first.
For example
A: How come he is picking first?
B:People that have ordered first will pick first.
上記の文は、どういうルールなのか、なぜ他の人が初めに選び取っているのか不思議に思っているかもしれない人に伝えると良いでしょう。
例文
A: How come he is picking first?
B:People that have ordered first will pick first.
A「どうして彼が初めに選んでいるのですか？」
B「先着順なのです。」
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