"Turn on the meter, please" is fine also. Alternative popular ways native English speakers would say this include the phrase "could you" which is a polite way to begin a question.
"Turn on the meter, please"(メーターを倒してください)でも大丈夫です。別の言い方としては、"could you" を加えるのも一般的です。これは質問をするときの丁寧な言い方です。
When travelling in a taxi the driver usually turns on or starts the meter to let you know how much the journey will cost you, if they don't do this then you might want to ask them to do it by saying 'can you turn on/start the meter please?'
タクシーに乗ると普通運転手はお客さんに料金が分かるようにメーターのスイッチを入れます。もし運転手がこれをしてくれなかったら、次のようにお願いできます。
'can you turn on/start the meter please?'
(メーターを倒してもらえますか)
"Don't forget to turn on the meter. " a term used very casually, 'don't forget to' can also be used as 'can you' in a more polite manner.
"Could you switch on the meter please." to 'switch on' is an expression of turning something on ex. "can you switch on the light" "Switch off the television, nobody is watching it."
"Don't forget to turn on the meter."(メーターを倒すのを忘れないでください)
= 非常にカジュアルな表現です。'don't forget to' は丁寧な 'can you'(~してもらえますか)としても使われます。
"Could you switch on the meter please?"(メーターを倒してもらえますか)
= 'switch on' は「スイッチを入れる」という意味です。
例:
"Can you switch on the light?"(明かりをつけてもらえますか)
"Switch off the television, nobody is watching it."(テレビを消しなさい。誰も見てないでしょう)
If a taxi driver forgets (or doesn't want) to turn on the taxi meter, then you may prompt them by making the exampled request above.
'Would you please...' is a great way of beginning a polite request.
タクシーの運転手がメーターを倒すのを忘れたら(あるいは意図的に倒さなかったら)、上記の文で、倒すよう促すことができます。
'Would you please...' は、お願いをするときの丁寧な言い方です。
This is a very simple yet polite way to ask the taxi driver to turn on the meter. They should do so or explain to you why they are unable to do so. I hope that this helps :)
Turn on' speaks of activating something, making something work.
For example, we can turn on the
-radio
-lamp
-computer
-stove
etc
When we enter the taxi we can kindly as the driver to activate the meter so it can begin charging our ride.