Actually, I feel a few of the other answers here (and even the question) are a bit simplistic: there's more to this issue than is indicated by the latest editions of the Chicago Manual of Style or Bringhurst's The Elements of Typographic Style. In lieu of a very long answer, let me point to the (long) Wikipedia articles on exactly this issue:
My (inadequate) summary would be something like the following:
The traditional typesetters' convention was to use a (single) longer space between sentences than between words. For instance, CMoS 1911 still recommends a 3-em space between words and an em-quad between sentences.
With the introduction of the typewriter (invented in the late 19th century), many typographical niceties were lost: the typewriters produced monospaced (fixed-width) text, and the only choice was between one space and two. Many people felt a single space wasn't sufficient to see the gap between sentences at a glance, so double spacing came into vogue.
Today, with proportional (variable-width) fonts, two spaces is no longer necessary, and can look distractingly too wide. Modern tools allow more choice than between exactly "one space" or two. In particular, TeX and LaTeX have got it right since the 1980s: they typeset a slightly longer space between sentences (though this can be turned off). HTML ignores multiple consecutive spaces anyway. (Sometimes fonts try to be smart and have the period character itself have a wider space following it, but this isn't ideal: there can be periods within a sentence, because of abbreviations etc.)
Even shorter summary (my opinion):
Don't use two spaces unless you're using a fixed-width font like a typewriter. If forced to choose only between one space and two, choose one. But if your typesetting system supports it, have a wider space between sentences.
After looking on the web, it appears that there is no single British rule that all British publications follow. If you look at what The Guardian (certainly British) actually does, it seems to change full stops into commas and leave them inside the quotation marks:
When Mike said 'Be careful what you wish for,' Janet listened.
The full stop turns into a comma (because it no longer ends a sentence), but it remains inside the quotation marks, indicating that this corresponds to a pause in the original quotation. This is what I would do, but I am American, and thus shouldn't be trusted on this.
However, some sites advocate that you use:
When Mike said 'Be careful what you wish for', Janet listened.
since there wasn't a comma in the original quotation.
The other answer links to the Oxford University Style Guide. This says
include punctuation which belongs to the quote inside the quotation marks, and a closing full stop/question mark/exclamation mark if the quote is a complete sentence.
If you take this literally as written, you would have to say:
When Mike said 'Be careful what you wish for.' Janet listened.
since 'Be careful what you wish for.' is a complete sentence. This looks wrong to me, but certainly much less wrong than:
*When Mike said 'Be careful what you wish for.', Janet listened.
I would hope nobody uses this last style.
Best Answer
The general rule of thumb is to abbreviate names as if they were ordinary words. The most common pattern in AmE is to shorten the name to its first letter and add a period:
Notable specifics:
C.
andJ.
even though non-name abbreviations tend to do so (e.g.U.S.
instead ofU. S.
)CCH Pounder
)e e cummings
)McD.
instead ofM.
(see the answers to How would you abbreviate surnames starting with Mc/O/D?)I know of no reason that BrE usage would differ from AmE usage but I encourage anyone who knows the BrE specifics to post them in a relevant answer.