What can vlc do
Play DVD/SVCD/VCD iso's / Images
If you have a DVD/SVCD/VCD packaged inside an image/iso file vlc can play this without you having to mount it or extract it in anyway. You can simply chose open file and pick the iso file. This is true for the standard .iso and .img files, not if its some proprietary format which is specific to a certain program (For example NERO's .nrg)
How to enable/use subtitles
Before you try to enable subtitles make sure the subtitles you have are in a format that VLC can read! You can find the list of compatible subtitle formats here. If VLC has detected any sort of subtitles available, you will be able to turn them on under the menu: Video->Subtitles track->Track 1
Auto detection of subtitles files uses a 'fuzziness' logic which you can specify. If this is wrongly specified you may end up with more subtitle file options than really exist or miss some that are provided. By default it allows any file in the right place which exactly matches the video name and may have some extra characters. If you are not seeing the number of subtitle options you expect you might want to allow more 'fuzziness' by changing the preference in video/subtitles/subtitle autodetection fuzziness where help is available if you 'hover' over the field.
If you mainly use .srt subtitles or .sub, you can get them turned on automatically when they are detected, by setting the Input/Codecs->Advanced->Choose subtitle track to 0, it will automaticly turn on the subtitle track. You can also experiment with the Choose subtitle language on the same page. But if u experiment a bit with the settings u should be able to get subtitles turned on automatically.
Note: On Mac OS X, the "Video->Subtitles track" menu item is permanently disabled for some reason. You must manually specify the location of the subtitles file in the "Subpictures" pane of the preferences.
Playing windows media files
VLC should be able to succesfully play both audio and video in wma and wmv 1 and 2, for the newest version (wmv3) only the windows version of vlc will be able to play it, since no opensource implementation of wmv3 have been made so far, so the windows vlc plays it by using the windows api. DRM files however can not be played on any OS.
How to adjust picture brightness/colors/contrast..
If you are using the wxwindows userinterface:
You can adjust the typical values to tweak the picture of your video source by turning on the extended GUI. This is done in the menu: Settings->Extended GUI. That will give you some extended control options for the video picture as well as an equalizer for the audio.
If you use Mac OS X or a skinned version of VLC: You need to enter the preference menu: Settings->Preferences. Once you have the preferences window open you go to: Video->Filters->Image adjust. Here you can adjust the different values. Note before they take effect you need to turn on the "Image adjust" filter in: Video->Filters
How to control the aspect ratio of the video
If ur source has a wrong aspect ratio (AR) or you wanna adjust the sources AR to your displays, you can tell vlc to override the source AR, and stretch or squeeze etc to get another AR.
If u use the cmdline you can control the ar by passing "--aspect-ratio x.xx". Where x.xx is an integer.
If u use the GUI, you can adjust the AR in the preferences dialog under video, in the field "Source aspect ratio".
I would advise you to use numerical values although the format 16:9 is also supported. Here follows some common AR's:
Fullscreen: 1.33 or 4:3 Widescreen: 1.78 or 16:9 Typical dvd: 1.85 Cinemascope: 2.35