We are getting many bug reports, please help us by being organized!
Read the known issues first (viewtopic.php?f=7&t=3636). If it is there, don't post it.
Search the Bug reports board. If your bug has been reported before don't post it.
Report only bugs from latest version.
Current version can be seen in the Releases board.
Report the bug as new topic into the Bug reports board. Watch out for other announcement posts like this.
Describe the problem as best as you can.
Ideally write down the steps to reproduce the bug.
It is also important to know, if it happens always, or it happened only once, or if it happens rarely.
Attach save and / or screenshot.
Saves are useful for crashes and complicated issues. Post a link to a 3rd party hosting solution (i.e. dropbox).
Attach a log file.
Log files help us find some of the harder to reproduce bugs.
The log file is found in your application directory, the filename is factorio-current.log.
Include your specific system information.
If the problem is system related, then write down your OS, VRAM, RAM, resolution, etc.