Before contacting the support check out the support page on the web. It may contain some last minute information (like solutions for recently reported issues) not included in this guide.
Please note, that the support is available in English only. If you use any other language, the support can handle that with using automatic translation, but the answer to you will always be in English.
For all non-trivial issues, the support will require a log file. You can speed up entire process by attaching that log file in your first contact with the support. To get the log file, use “Show Log Folder” option in “Setting” / “Log Level” menu. This will open the Finder with the log folder set and the log file selected. The name of that file is ArchCommander.log.