Getting help from the community
Slic3r's got a dedicated section at the official RepRap forums.
You can also enter the FreeNode IRC #slic3r channel to chat with other users and get help (don't forget there's an excellent #reprap channel too).
If you have a bug to report (but make sure it's a bug), use the GitHub issue tracker. If you're in doubt, please consider discussing it on the forums or the IRC channel before reporting it. When you file the report, provide as much information as you can: link your STL files and your configuration, and explain what's wrong in the results you get (screenshots often say more than a thousand words!).
Writing to the author is a nice thing, but he gets too many e-mails so he apologises in advance for not being able to answer in a timely manner to helpdesk questions.