Please check out my first tutorial about how to set up a Minecraft Server (mainly for Mac OS X) here: www.planetminecraft.com/blog/mac-creating-a-server---part-1/
Part 3: www.planetminecraft.com/blog/hating-multiplayer-servers/

This blog is a continuation of my first blog, which is how to set up a Minecraft Server (maily for Mac OS X). This blog covers both Windows 7 help and Mac OS X, but I base it off of Mac OS X.


How to install Plugins for Craftbukkit:
This might sound complicated, but it really isn't. If you did follow what I did in my first part, then this should be very easy for you. If you did make a craftbukkit server, then there will be a plugins folder inside your Minecraft server folder. That is where you download and place your plugins. Do get a plugin, go back to bukkit.org/ and click 'Get Plugins' which is located on the top right hand corner of the screen. If you wish you can click 'Bukkit Dev' then click 'Server Mods' at the top left hand corner of the screen.
Either way, you will get a list of plugins which are arranged by when they were updated. Simply click one of the plugins which sound interesting, and it will bring up a new tab. The tab will have more detail about the plugin and a download link. Download it to your plugins server, and restart/reload your server. If the plugin requires it, then there will be extra files. Most plugins work together just fine, but some don't.

Updating your Server:
To update your server, go to the same places where you got your plugins, or even your craftbukkit.jar/minecraft_server.jar. Download them and replace them old ones with the new ones. You may need to stop your server. You for sure will need to restart/reload your server too.