Need advice on using punctuation in quoted speech, thanks teachers!

[Help Wanted]

I am confused as to when I need to insert a comma or a period in a quoted speech.

For example:

"Mr Smiths, can you serve me first, please?" Tom asked.

"You'll have to join the queue, Tom," said Mr Smiths. ( Should I put a comma or a period after Tom?)

"Be quiet! Young people must learn to wait," one of the customers said. ( Same question...Should I be putting a comma or a period after the word "wait"?)

Please advise, teachers , thanks very much!

[Casiopea]

Punctuation goes inside the quotation marks:

"Mr Smiths, can you serve me first, please?" Tom asked.
"You'll have to join the queue, Tom," said Mr Smiths.
"Be quiet! Young people must learn to wait," one of the customers said.

[Help Wanted]

"You'll have to join the queue, Tom," said Mr Smiths.
"Be quiet! Young people must learn to wait," one of the customers said.

So, why do we put a comma after the word "wait" not a period? What's the difference between putting a comma and putting a period after the word "wait"?

Please advise, teachers! Thanks a million in advance, Help Wanted urgently!

[Tdol]

The reason is the speech you are quoting is a part of the sentence, which ends with 'one of the customers said.'. Otherwise, you'd have 'One of the customers said.' as a complete sentence, which would automatically beg the question 'What did they say?'.