This tutorial series is designed for a quick introduction to programming in C# using Unity. It will briefly introduce most of the language features, but from the perspective of use within Unity rather than general use cases, and hopefully therefore will be more interesting to learn from. I will be writing with the assumption that you already have Unity and have a basic understanding of the program.

How to get started?

You will need a copy of Unity 3D. Unity comes bundled with a copy of MonoDevelop, which I will use for programming, although you are not required to use that code editor. You can get a copy of Unity at unity3d.com . Note that while I will attempt to make sure the examples here remain future compatible with all versions of Unity, some things may slip through the cracks. If you find that a feature or example isn’t working, you can always go back to older versions of the program here http://unity3d.com/unity/download/archive
Once you have Unity downloaded and installed, you may want to consider browsing Unity’s own set of tutorials at http://unity3d.com/learn/tutorials/modules

Why C# versus another language?

Ultimately, it is because it is the language I am most familiar with, although there are a lot of other arguments you will find posted around the web. I haven’t spent a lot of time with JavaScript and I have heard that the version used in Unity is not true JavaScript anyway. Boo is another language option, but I almost never see any examples or tutorials in that language and have heard that Unity is not going to include it in any documentation for Unity 5. Most serious developers I have spoken with seem to prefer C#, and that stat is confirmed by this thread on the Unity forums comparing the language options. It shows C# is more than twice as popular as any other option:
http://forum.unity3d.com/threads/boo-c-and-javascript-in-unity-experiences-and-opinions.18507/

Where can I learn more about C#?

For those of you afraid to google, here are a few convenient links…
http://msdn.microsoft.com/en-us/library/aa288436(v=vs.71).aspx
http://www.tutorialspoint.com/csharp/csharp_overview.htm
http://www.csharp-station.com/tutorial.aspx
http://www.learncs.org