comma after introductory adverb or conjunction: when is it needed?

[WordsNStuff]

Reading through some comic books, comic strips, movie subtitles, and video game subtitles, I noticed some inconsistencies in regards to putting a comma after the introductory word of a sentence, especially when it begins with a conjunction. I have tried looking for an answer online, but it seems to be about 50-50 whether it is necessary or not.

Take this dialogue for example:

So when do we need to go?
Well the movie doesn't start for another hour.
Then we should leave pretty soon.
But the theater is very close to here.
And are we going to get dinner?
First I need to find my keys.
Next I need to find my coat.
Now go find them and meet me outside.

Perhaps not the most proper conversation between two people, but that's not the point. Which of these sentences needs (or at least should have) a comma after the first word? Are there any sentences here where it is correct to keep the comma omitted?

Sorry if this was already answered in another thread. I tried searching for it before posting this and came up short.

Thanks in advance.

 

[entangledbank]

It's never necessary; they never need it; it's always correct. Commas are often unimportant in marking the structure of English sentences. Use it there if you say a break there, don't if you don't. It makes no difference to grammar or meaning; it might make a difference to intonation.

 

[WordsNStuff]

Thank you for the quick reply.

You say it is always correct to leave them off, but does that also mean it's incorrect to put them in (where needed)?

 

[iskndarbey]

She also said it's always correct to put them in in that context. Put them where you want a pause, don't where you don't.

 

[OzziBoy]

You say it is always correct to leave them off, but does that also mean it's incorrect to put them in (where needed)?

As iskndarbey replied, it is both correct to have them in and correct to have them out in your sentences.

Be careful though, commas can change the meaning of a sentence dramatically ...

Let's eat grandpa. - This means that you want to actually your dear old grandfather.
Let's eat, grandpa. - This is you telling your grandpa, "let's eat."

 

[Nunty]

Just a small observation: "comic books, comic strips, movie subtitles, and video game subtitles" may not be the best source for verifying rules of punctuation. Space (measured in number of characters) is an important consideration there, among others.