Fix your subtitles, today!
Before you start, you have to load a subtitle and a movie. Use the menu: File - Load subtitle or just click Ctrl + O If your movie has the same name as your sub and is in the same directory, you will notice that the movie automatically loads. If not, just use the menu again: Movie - Open or Ctrl + P
1. Adding a delay
When you notice that in the beginning of the movie your sub for instance comes two seconds too early and it still comes two seconds two early at the end of the movie, you need to set a delay. You do this by going to the menu: Edit - Timings - Set delay or click Ctrl + D

Because the sub comes two seconds too early, you use + 00:00:02,000. When your sub comes too late, you just use - instead of +.
2. Difference between FPS & input FPS
Input FPS is the Frames Per Second of the movie that the subtitle was originally made for, thus not for your movie.
FPS is the FPS of your movie, where you want to adjust the subtitle to.

When you load your movie the FPS and the input FPS are automatically filled in. The FPS is always correct, but the input FPS automatically gets the same framerate and it could be that it isn't the correct framerate.
If you for instance have a movie with framerate 23,976 but you downloaded a sub made for a movie with framerate 25, you just set "input FPS" to 25 and "FPS" to 23,976.
When you save the sub, it's automatically saved with a framerate of 23,976 in this case !!
3. Synchronise subs or better adjust timings
Subtitle Workshop can synchronize subtitles to a video by three methods.
Method 1: first and last dialogs
Play the video until you reach the first spoken dialog or the first place that should be subtitled in the movie, and when you hear/read it, press the "Mark as first dialog in video" button or the [Alt]+[F] keys.
Seek to the near end of the video and when you hear/read the last spoken dialog or the last place that should be subtitled, press the "Mark as last dialog in video" button or the [Alt]+[L]

After you have followed this steps, click the "Edit - Timings - Adjust subtitles..." or the [Ctrl]+[B] keys.
Method 2: adjust to synchronized subtitles
I find this the most accurate and easy method, but you don't always have a sub synchronised with your movie ... but worth searching for it, even if it's in another language.
So, it is useful if you want to quickly adjust your subs to an already adjusted subtitle file in another language. This method will work even if both files have a different number of subtitles, the only requirement for proper adjustment is that first and last subtitles in both files correspond.
You just have to click the Timings - Adjust to synchronized subtitles menu or press the [Shift]+[Ctrl]+[B] keys, and load the synchronized file.
Method 3: synchronize using two points
This method is not as precise as first method but will work very well in most cases. It works by taking two points of the subtitle file and two points of the video, and calculate the times using a linear algorythm. For more info, see the help file of subtitle workshop.
4. Split or join subs
Splitting 1 sub into 2

You first have to choose where to split the file, you have 5 possibilities:
1) Split in selected item
The subtitle file will be split right after the item that is selected in the main window.
2) Split in item number
The subtitle file will be split in the item you select.
3) Split in given time
The subtitle file will be split in the first subtitle which's initial time is greater than the time you select.
4) Split in given frame
The subtitle file will be split in the first subtitle which's initial frame is greater than the frame you select.
5) Split in end of video
The subtitle file will be split in the first subtitle which's initial time is greater than the time in which a video ends (the video's duration).
After selecting where to split select the file names (excluding the extension, it will be added automatically), the output format and press the Split button.
Check "Recalculate time values" if you want Subtitle Workshop to automatically set a delay to the second subtitle so you don't have to do it manually after spliting. Finally select the output path, the output format and press the Split button.
Join subtitles
With Subtitle Workshop you can join more than two subtitles, and those subtitles may be in different formats, time or frame based, and if frame based, they even may have different FPS! Click the Tools - Join subtitles... menu or press [Ctrl]+[J].

Now press the Add button and add all the files you want, in the correct order. If you made a mistake in the order of one file you may drag it with the mouse and put it where you want. If the file is a frame based subtitle you may also modify it's FPS selecting it and modifying the value of the combo box that is at the left of the "Clear" button. After this you need to select the output format. If you want to load the resulting file, check the "Load file after joining and saving" check box. Check the "Recalculate time values" box. Finally, press the Join button.