Ads adding problem!

Hello.

First of all, i wanna say that i found sound interesting answears on this forum and for this i thank you.

I am a fresh student of Unity, and i still have a lot to learn but a have a situation.

I can't make any ad to work, no matter what the provider is.

I know i have to create a new game object and write some code lines... but i seems i can't get the codes right...

Are there some general steps or can you give a a specific step by step tutorial on adding some ads that worked for you.

I am ussing Unity 4 pro version.

I am trying to export for the android market!

Thank you all!