[King Kovifor]

mihai11,

First you need to know PHP to develop plugins. There are several PHP resources out there, including:

http://www.php.net
http://www.w3schools.com

There are many more, but I can't think of them off the top of my head. A google search could help you a lot.

The next step would be to read the forum EnIgMa1234 has linked to. Specifically the following threads:

http://www.vbulletin.org/forum/showthread.php?t=82923 (you should start here)
http://www.vbulletin.org/forum/showthread.php?t=82625 (Writing)
http://www.vbulletin.org/forum/showthread.php?t=92953 (Managing Products)
http://www.vbulletin.org/forum/showthread.php?t=82882 (who's online setup)
http://www.vbulletin.org/forum/showthread.php?t=119933 (templates)

After you write your plugin, you may advance your skills within vBulletin by learning the vBulletin classes and functions. You may find these here:

http://members.vbulletin.com/api/

Also, if the API's explanation doesn't help you, try reading this thread:

http://www.vbulletin.org/forum/showthread.php?t=98009

If you plugin doesn't work, you may want to read this thread about debugging it:

http://www.vbulletin.org/forum/showthread.php?t=151288

If you work with custom templates, be sure to cache them. Instructions can be found here:

http://www.vbulletin.org/forum/showthread.php?t=104532