no. if but before is a sentence on its on and after but is a sentence on its own then put a comma before but.
after
befor
Before. ex. I had every intention of going to the store, but I forgot.
Punctuation is dictated by the meaning of your sentence, not by the presence of particular words. A comma indicates a brief pause. Say your sentence aloud, and where you find that you naturally pause briefly, you will probably find that a comma is appropriate. Other people may punctuate the same sentence differently. That is not necessarily wrong. A lot depends on the context: whether it is formal, informal, written, spoken, and so on. Here are some examples: 'There was nobody in the house but my mother.' (No comma) 'I like cheese, but my sister can't stand it.' (Comma before 'but') 'I would prefer you to stay at home but, if you do go out, please wear a warm coat.' (Comma after 'but') 'I would prefer you to stay at home, but if you do go out, please wear a warm coat.' (Comma before 'but') (The last two examples convey slightly different shades of meaning.) It's perfectly possible to have a comma both before and after the word 'but' if you think the sense requires it, but you should be wary of having too many commas in one sentence.
No, before ... as in: Marcus Welby, MD
Yes. You should write it at John P. Doe, MD
Not necessarily. Commas are a feature of sentence structure.
Yes, you should use a comma before "Jr." when writing a person's name to separate the person's last name from the suffix. For example, "John Smith, Jr."
The comma should come before the word "but" when it is used to separate two independent clauses. For example: "I wanted to go to the store, but it started raining."
before
No, a comma is not necessary.
no
no
no
You would use a comma before it. Xerox, Inc.
I do not use a comma before and after that word, therefore you will not see it in any sentence I have written.