The first thing to remember is that the people who actually make the corrections you suggest are very experienced, and are used to seeing lots of different types of errata reports. So the exact format of your report isn't really very important--just get the report to us in any clear form that we can understand.
Beyond that, here are some tips to avoid misunderstandings.
It's always helpful if you report the full title, etext number, year and filename of the text you are correcting. We have multiple editions and versions of some texts, like Homer's "Odyssey", and unless you tell us exactly what text you mean, we may have to spend some time searching and guessing.
Especially, please check and report the exact filename of the text. It is amazingly common for people to report problems with abcde10.txt, when abcde11.txt is already posted, and has these and other errors already fixed.
When there are only a few errors, it's usually easiest to cut and paste the line or lines where the error is into your e-mail, with your comment.
It can also be useful to give the line number of the place where the error is, and some people who check texts regularly do this. If this seems natural to you, do it; if it doesn't, don't.
An ideal report for a typical errata list might look like:
Title: The Odyssey, by Homer
Translated by Butcher & Lang
April, 1999 [Etext #1728]
File: dyssy08.txt
Line 884:
back Telemachus, who bas now resided there for a month.
"bas" should be "has"
Line 1491:
Ithaca yet stands. But I wouldask thee, friend, concerning
"would" and "ask" are run together here
Line 1563:
in his father's seat and the elders gave place to him
This is the end of a paragraph, and needs a period at end.
Line 15346-7:
'Hearken to me now, ye men of Ithaca, to the
will say. Through your own cowardice, my friends, have
I think there is something missing between "the" and "will"
But the following would get the job done as well:
In Homer's Odyssey, translated by Butcher and Lang, from /etext99,
file dyssy08.txt, I found the following errors:
Telemachus, who bas now resided
change "bas" to "has"
But I wouldask thee,
"would ask" run together
and the elders gave place to him
needs period
ye men of Ithaca, to the
will say.
line missing between "the" and "will"?
Where there are more than, say, 50 changes, it may be easiest all round just to submit a corrected version of the file. However, if you do this, please do not re-wrap the paragraphs unless it is absolutely necessary (and I can't think of a case where it might be, since we can re-wrap texts too); we need to check your suggestions before reposting, and if the file is very different, it is difficult and time-consuming for us to find your real changes among all of the changes in the lines. Instead just add a comment in your mail like "I think this text needs rewrapping."
If you are a regular, and have used any of the standard Gutenberg tools like Gutcheck or Guiguts to find errors, please don't list these in your mail. We will be running gutcheck and a basic spellcheck as standard on every updated text that we repost, and it just wastes time to have lots of duplicates. You might just mention something like "gutcheck finds a lot of bad quotes"; we'll know what to do from there. Please concentrate your report on the errors that we won't find, or might miss, with a standard automated scan.