All software has bugs, but together with your help we can get rid of them as fast as possible. One of the fastest ways to do this (and make Kdenlive better) is to make sure that the developers spend as much time as possible fixing bugs rather than trying to figure out basic details in bug reports like what the problem actually is and when it happens. When you provide this information in your bug report, you increase the chances and speed of it getting fixed for you, and free up developer time to work on the great new features that you would love!
Where to report 
Use mantis to report problems and wishlist items.
Content of the report 
Here's the information that can help the most and how to provide it (it's also a good idea to include the title as well, so developers can quickly scan for the information they need):
OK, this is pretty obvious, but the more clear, and detailed you can make the description, the better we know what you're talking about.
Try and use the actual names of features / menus / windows you see in the application (eg Project Tree, Help -> About Kdenlive).
Try to describe what you see and what you expected to see.
NOTE: Only include one issue or wishlist per report. It only takes one more click to open a second and also ensures that none of your issues get missed.
After the description, the most useful thing you can provide is what's known as a backtrace. It's kind of like your computers description of what happened.
- If you installed with the Builder Wizard, then when kdenlive crashes it should ask if you'd like to review the log. Just say yes and copy the text it shows (all of it) and save it with a text editor like kate or gedit. Give it a name that describes the crash and your user name in a couple of words and upload it on your bug report using the "Upload files" button.
- If you installed by another method, you can follow the steps here.
Your problem may have already been fixed, so providing the version of the software you're using is important.
- If you installed packages, name what distribution you're using with the version (eg Kubuntu 8.10, Mandriva 2008 etc) and where the packages came from. You can get the version number from the Help ->About Kdenlive menu (eg 0.7).
- If you installed using the Kdenlive Builder Wizard, you'll have a folder called "Bin" that has your kdenlive binary that you run. Navigate to that folder in the command line (or in Dolphin and then push the f4 key), and then type:
You'll see something that looks a bit like this:
Kdenlive Builder Wizard version: 0.7.0 ffmpeg: Revision: 15918 Last Changed Date: 2008-11-23 14:36:44 -0500 (Sun, 23 Nov 2008) mlt: Revision: 1240 Last Changed Date: 2008-11-17 00:57:32 -0500 (Mon, 17 Nov 2008) mlt++: Revision: 1240 Last Changed Date: 2008-11-06 00:32:23 -0500 (Thu, 06 Nov 2008) kdenlive: Revision: 2722 Last Changed Date: 2008-11-23 14:34:31 -0500 (Sun, 23 Nov 2008) Qt: 4.4.3 KDE: 4.1.3 (KDE 4.1.3) Kdenlive: 0.7
Just copy the whole thing into your bug report.
Steps to Reproduce: 
This should be a numbered, one step per number guide that could walk someone who had never used Kdenlive before through to see the same problem. EG:
- Imported clip using the "Add Clip" button.
- Dragged a clip from the Project Tree tab to the timeline.
- Dragged the "oldfilm" effect from the effect list onto the clip in the timeline.
- Press play on the project monitor tab.
- No effect appears.
Playback / Rendering Testing: 
If you installed with the Builder Wizard or by compiling from source, and your issue has anything to do with video playback or rendering, it's also useful to see if these can be played properly by the two pieces of software Kdenlive uses.
Navigate to the bin folder where the kdenlive binary is in the command line and copy the following (replacing the path, with the path to your video file):
Both of these should play your video file properly. If they don't (and even if they do) let us know this in your bug report, along with any errors you see in the command line.