A rather extensive FAQ is available at the SH/SC Wiki.

General

Is foobar2000 still under active development?

Yes. Please see the forum and the foobar2000 homepage for the latest version and news about upcoming versions.

I have Windows Vista and my foobar2000 has stange behavior. Do you plan on fixing those bugs soon?

Foobar2000 already fully supports Windows Vista. Some components do not. Try to look for the latest version of those third-party plugins as they might get fixed soon.

I'm looking for a specific feature. How should I know if a third-party plugin suits my needs ?

If you are not the Ctrl+F kind of person with your web browser, this is the perfect opportunity for you to get familiar with it. Go to the components section, press Ctrl+F and search for keywords related to what you are looking for (yeah, like google). You will hopefully find something that suits you. Otherwise, maybe you can make a request in the foobar2000 forum or even better, code it yourself then share it with the community!

Playback

There are multiple output methods available: DirectSound, waveOut and Kernel Streaming. Which one should I use?

The default setting (waveOut) is recommended; it should be safe to use anywhere. Using DirectSound results in better performance (less CPU overhead)—especially under Windows 2000, Windows XP or newer—but there shouldn't be any audible difference between the two. In certain rare cases, Kernel Streaming may produce better results than DirectSound/waveOut (if for some reason you need data sent through digital out to be bit-identical to source stream); however, bit-identical results with DirectSound have been reported on soundcards capable of mixing multiple streams in hardware (with hardware mixing enabled in DirectSound settings).

Please note that Kernel Streaming is an experimental feature with known issues, and using it is not recommended unless you have a clear need to do so. Most of perceived "sound quality differences" between DirectSound and Kernel Streaming are related to the fact that Kernel Streaming usually bypasses the Windows volume control. In addition, Kernel Streaming only works on Windows 2000, Windows XP or newer.

How can I send my files from Windows Explorer into a specific playlist, so as not to erase my current playlist?

Preferences → General → Always send to playlist (playlist name)

Why can't I listen to unfinished downloading files?

Foobar2000 needs exclusive access to the file. A good workaround is to copy the unfinished file, then try to play it.

Look & Feel

I just saw a great looking foobar2000 window, but I don't know how to get mine looking the same way! Is there no hope for me?

Of course there is! First take a look at those threads and get in touch with what other users achieved:

Then, you are ready to give it a try! You can find some of the user's configuration in the links below. Note that Single Column Playlist and ColumnUI are standalone components that you need to download.

Is there a way to make my instant messenger's "Now Playing" show the song I'm listening to with foobar?

Yes, through plugins:

AMIP Complete now-playing plug-in for mIRC, PIRCH, Klient, Bersirc, other IRC and Mail clients, supporting full player control from mIRC, playlist search, clipboard integration, HTTP, dynamic image signatures, etc.
for MSN
for Miranda-IM

I have seen some people using something which pops up to display the song being listened to. Where can I find it?

It's called foo_prettypop. Note that it requires the .NET Framework to work.
If you are using Columns UI, it has a popup notification feature too ("Preferences -> Display -> ColumnsUI -> Status Bar/Systray (tab) -> Show popup notification baloon")

Is there a way to map my multimedia keyboard keys?

You can assign actions with keys including multimedia key from the in "Preference -> General -> Keyboard Shortcuts". If it still does not work, take a look at this tutorial.

Columns UI

How do I know which component is meant to be used with Columns UI?

Component section of the wiki shows which plugin you can use for ColumnsUI's interface.

How can I get tabbed panels?

Use uie tabs.

Where are the options for changing the playback buttons?

Right click on buttons area → Customise...

How can I display the album art and cover above my playlist?

To set the panels above your playlist, just use list all toolbars, then add the panels/toolbars/visualizations that you want to use. Organize them as you want them to be displayed. And finally, use the 'minimum height' values of the corresponding panels. As it is not a common way to use the toolbar, you may experience some unexpected behaviour. Keep in mind that it may create some display problems. Musicmusic may fix this into the next version of Columns UI.

I have more questions.

Refer to the offial ColumnsUI FAQ.

Database, Tagging & Album Cover

Foobar always takes between 5 minutes and several hours to open all the files in the same playlist. Is there a way to reduce this delay?

0.8.x

Sure. Enable the media (Preferences → Core → Database). You will be able to add thousands of files in only 30-40 seconds.

Alternatively, if you don't want to activate the database, just save your playlists in the fpl format.

0.9.x

Database is now known as Media Library ("Preferences → Media Library") and there is no way enable/disable it.

I updated my tags, but foobar still shows the old tags. How can I fix this?

Select the file(s), right click on any of them, go to Tagging, then click on "Reload Info from File(s)".

How to guess tags based on directory structure?

Select all tracks in the playlist → right click → open the "Properties" dialog → chose "Fill Values from File Names" from its context menu.

Is there a way to have album covers downloaded automatically?

Unfortunately, it is not possible. But, there is a way to be 2 clicks away from those cover arts. Take a look at this thread for more info.

Troubleshooting

I get an error message saying "referenced file doesn't exist" on the console. What does that mean, and how can it be fixed?

This error is caused by an outdated/broken CUE sheet or APL link. You need to find and repair or remove it. After that, run "Remove dead entries" from the Database page in the Preferences dialog.

The Album List shows dead entries after restarting, even though I used "Remove dead entries" earlier. Why is that?

The files are probably still referenced in one of your playlists or in the history (if you are using an old version of foo_history). Use Playlist → Remove dead entries from the main menu on all your playlists, or remove the dead entries manually. As long as the files are on a playlist, they will be in the database and thus will show up in album list.

Menu items for some plugins don't show up. I reinstalled but I still don't see them, even though the plugin is shown as a Loaded Library.

If you delete a menu item for a plugin, and then re-add the plugin, it won't re-add the menu items. The solution is to open the Preferences dialog, go to "General → Keyboard Shortcuts" and add the items manually.

An MP3 does not play properly (there is no sound) in fb2k whereas it plays perfectly in other players. What is the problem?

You need to disable Use peak info to scale down tracks that still clip after applying replaygain in the Preferences dialog, in the ReplayGain section of the Playback page.

I use the volume control toolbar but it doesn't work. What's the problem?

You may be using Kernel Streaming or ASIO. These two output methods are not compatible with the volume control toolbar.

There is always a long delay before changes to the DSPs take effect. Can I reduce this?

Try reducing the output buffer length from Preferences → Playback → Output → (your selected output method). However, do not put it at the minimum length. 300ms should be enough (more if you are using several DSPs).

What are metadb_handle leaks?

metadb_handles are resources used in the metadata management in foobar2000. A leak indicates that a component does not release them (in time). The overall effect of such a leak is relatively harmless. Nevertheless, this is a programming error and foobar2000 detects and reports it to the user. Unfortunately, it is not possible for foobar2000 to detect which component caused the leak.

I hear static when fading in/out - pause/unpause.

Be sure you have the latest sound drivers installed and disable your dsp's before reporting it. Some users reported that using Kernel Streaming instead of the default output fixed the problem ("Preferences -> Playback -> Output"), but be aware that this plugin is still experimental and it is issue related in some cases.

Foobar2000 and other players

Is foobar really better than Winamp?

There is no set answer. According to public opinion, foobar is great for people wanting a minimal player, as well as the opposite: people needing advanced features. However, the medium users are lost between the profusion of settings and components to find. Some relevant links:

Is the sound really better with foobar?

As the author of foobar says himself, foobar doesn't have a better sound than the other players like Winamp. From a theoretical point of view, the sound from foobar2000 is not different from the sound from other players since a player can't improve the sound drastically (though it might be altered if not correctly set). Your hardware is much more important (audio card, speakers, headphones, even cables), as is the audio source (Audio CD? Lossless codec? Lossy codec?). The software part is only secondary.

Even if sound modifiers (DSPs) are used, they only widen the gap between the source and the result, which might actually degrade the sound quality.

I won't leave iTunes, it manages my iPod perfectly!

Maybe this will change your mind: foo_dop.