It's clear from the response to this post that many people are still having problems using the Video DownloadHelper extension in Firefox on Macs. Since a slightly simpler solution has emerged since it was written, here is a crystal-clear guide that may make it easier for some users.

1. Download ffmpegX into a folder on your Mac:

2. Double click on the DMG file. Right click on the ffmpegX icon and select "Show Package Contents":

Along all these years as software reviewer I've come across many applications that let you download videos from YouTube and other popular online video websites. But it wasn't until yesterday that I tried out a handy little Firefox add-on called Video DownloadHelper, and after only a few hours of usage I've already decided this is the only app I'll ever use to download YouTube videos.

Video DownloadHelper is installed just like any other Firefox add-on. After the ubiquitous Firefox restart you'll notice a new button on your Firefox toolbar that will light up with colors and move every time you're on a web page with embedded videos. Click the button and you'll access download links for all the videos included in the page, both in FLV and MP4, as well as a series of available actions for each selected video. There's also an icon beside the video's title that lets you access the same menu. All you have to do is click the link of the video you want to download, and you'll be prompted for the target folder. That's all!

But what about all those other options available in the context menu? They let you perform several different actions with the selected video, besides downloading it straightaway to your hard drive:

Download & Convert - Helps you convert the selected video to a handful of formats, including WMV, iPod and iPhone, 3GP, MOV and AVI. This tool requires the installation of a third-party video converter - ConvertHelper, also developed by the Video DownloadHelper guy. You can easily get this tool in the extension's settings menu: go to Tools > DownloadHelper > Preferences and then click the Conversions tab.

Tweet this video - Lets you send a message about the selected video to your Twitter account. You need to fill in your Twitter credentials (username and password) in the extension's settings menu, inside the Services > Twitter tab.

Copy URL - Copies the video's URL to the Windows clipboard so that you can use it elsewhere. Note that this option doesn't copy the standard YouTube URL you see on your web browser, but the address that points to the actual video file - either in FLV or MP4.

Add to black list - This option enables you to add certain websites to a blacklist and thus block them from appearing on the list of available media generated by Video DownloadHelper. It's a smart way to avoid advertising videos, for example. You can also check the complete blacklist in the settings menu.

Send to mobile phone / Send to locker - Lets you upload the selected video (or only its audio stream) to your mobile phone or your personal web locker via a special online service called MP3tunes. You need to set up an account though. Video DownloadHelper lets you create one in the Services > MP3tunes tab inside the settings menu.

My favorite tool for downloading YouTube clips on Mac is the DownloadHelper extension for Firefox. It's convenient, quick and even converts videos into the format of your choice while it downloads. For a while however I've been plagued with a "Conversion requires external application" error message when downloading certain clips.

The exact error read: "Conversion requires an external application that appears to be missing on your system. Configure conversion? > Cancel > OK." When I selected OK, it opened the Preferences for DownloadHelper highlighting in red the location path for the selected converter option which is either FFMpeg or MEncoder.

I eventually found the start of the solution was to install the ffmpegX video/audio encoder for Mac. ffmpegX is basically a Mac OS X graphic user interface designed to operate more than 20 video and audio processing tools including ffmpeg which is a very fast video and audio encoder.

For the purposes of correcting the DownloadHelper error, you don't actually need to use the ffmpegX interface. You do however need it to use it to install the mpeg2enc binary for ffmpegX. Once you've installed ffmpegX, you'll be immediately taken to the main interface where you'll be prompted to load 3 binaries. You only need to load one binary to fix DownloadHelper - the mpeg2enc binary - which can be found here.

You don't have to worry about the mencoder or mplayer binaries but you do need to check the box next to mpeg2enc and locate the binaries that you've downloaded onto your hard drive. The resulting installation places the binaries in your Mac's application support library. The final step is to re-open your DownloadHelper preferences (in Firefox's Tools menu) and enter the path where the binaries are located. For most people, it will be "/Library/Application Support/ffmpegX":

When the DownloadHelper logo animates next to the URL bar while you are using YouTube, you should now be able to download videos again with it. However, it hasn't worked perfectly for me. For some reason, videos are being downloaded to a temporary file on my Mac rather than the directory I've configured downloaded files to be saved in DownloadHelper. In addition, the files are not being converted to QuickTime format they were previously. However, I can sort-out all of this by manually moving the files and converting them myself later. The important thing is that this work-around allows you to download YouTube clips again using DownloadHelper.

YouTube has certainly caused a revolution in the way we enjoy content on the Web. A few years ago we used to waste a couple of hours every day surfing channels on TV. Now we spend that time on the computer instead, watching all sorts of online videos. So, if you want to make the most of your personal YouTube experience, have a look at this list of tricks and tips for the popular website, with which you'll be able to set starting points, extract audio tracks or even play videos at different speed rates.

Specify a starting point for videos

Say you send a YouTube video to a friend and ask him to fast forward to the funny scene at 03:52. He'll probably have to wait for a while until he can watch those frames.

Luckily you can now use this simple trick: add #t=XmYs at the end of the video URL – where X stands for minutes and Y for seconds – and the video will start right at that point. So for example, #t=3m52s is the parameter you'll need to add to that video you wan to share with your friend. Nice, huh?

Extract the audio track to MP3

Youtube features many videos in which the important thing is sound, not images. Downloading the whole FLV video just to get the sound is not the best solution, so why not simply download the audio track and save it as an MP3 file?

This is what you can do with VidToMP3, an online ripping tool that's very easy to use: all you have to do is copy and paste the URL of the video you want to extract the sound from and download the resulting MP3 file. If you prefer a desktop solution, then use FLV Extract to split the selected video in image, sound and source code.

Play videos at a faster or slower rate

Unlike traditional desktop video players, YouTube doesn't feature speed controls with which to speed up the boring parts of a given video or play an important dialog at a slower speed. In these cases, you can use MySpeed, a simple tool that runs in the background and displays a speed slider every time you load a YouTube video on the browser.

Play videos at full screen

For those occasions when you want to focus on the video and forget about comments, stats and other distracting elements on the website, watching videos in full screen is the best solution. You can use the appropriate button on the embedded player or use the v/ parameter instead of watch?v= to link directly to the full screen version. So http://www.youtube.com/watch?v=A_EgbJFSAQM would then be http://www.youtube.com/v/A_EgbJFSAQM

Always bear in mind that a full screen video may lose image quality compared to the smaller version. But if you combine this function with the HD one, the results can be impressive!

Download videos to your hard drive

YouTube doesn't feature any tool to download videos to your computer, but there are dozens of software tools and online services that enable you to download your favorite videos, play them as FLV files and even convert them to other formats.

You can choose between desktop apps like vDownloader or aTube – including also easy tools like YouChoob or Firefox add-ons like Video DownloadHelper – or online tools such as VideoDL, Vixy or KeepVid. If you're looking for a desktop player, you can try FLV Player or FLVPlayer4Free.