Please see the Emacs manual for information on how to report bugs. See Checklist for Bug Reports in The GNU Emacs Manual.
Sending bug reports to the help-gnu-emacs mailing list is undesirable because it takes the time of an unnecessarily large group of people, most of whom are just users and have no idea how to fix these problem. The bug-gnu-emacs list reaches a much smaller group of people who are more likely to know what to do and have expressed a wish to receive more messages about Emacs than the others.
If you have reported a bug and you don’t hear about a possible fix, then after a suitable delay (such as a week) it is okay to post on the help list asking if anyone can help you.
If you are unsure whether you have found a bug, consider the following non-exhaustive list, courtesy of RMS:
If Emacs crashes, that is a bug. If Emacs gets compilation errors while building, that is a bug. If Emacs crashes while building, that is a bug. If Lisp code does not do what the documentation says it does, that is a bug.
Anything sent to firstname.lastname@example.org also appears in the newsgroup news:gnu.emacs.bug, but please use e-mail instead of news to submit the bug report. This ensures a reliable return address so you can be contacted for further details.