Turdburglar wrote an excellent guide for how to write your own AI for sc2.

http://sc2.nibbits.com/articles/view/10/writing-your-own-starcraft-ii-ai

Hope you can find some info there

Thanks for the reply people, I'm developing my first AI now.

O ya, about scouting, how do i make a unit wanders around an opponent's base instead of running around the whole map?

Lol Eskimo, I'm not talking about the player itself, what i meant was how to make the AI wanders around an opponent's base, which function should i call, and if it's possible, can i design my own route?

Yup, I also want my Ghost to come near to enemy base but don't "Attack", so he can cloacked and using "Nuke" on enemy base. So the probem here is how to make them stop the attack function when they near the enemy base and using other command, or using at the appropriate place ( ex : Dark Templar will not attack the army defense outside and attack the worker inside the base instead, harassment force will focus on the enemy worker, rather than attack building ( only when necessary ))

I also wonder about the code of the scout, ( don't know where it from) how to make them close to the enemy base but don't come near them. It will good to gather a big force in front of enemy base than attack , rather than come one by one .

 I don't know too , but instead i using AITechCount Function, so you can count how many unit has been built or in Progress.
    For example.   
  AITechCount(player, c_PB_Gateway, c_techCountCompleteOnly ) >= 2
  && AITechCount(player, c_PB_Gateway, c_techCountInProgessOrBetter ) <=3

That mean already have 2 gateway are build and 1 gateway are in build progess

   You can use AITechCount for unit and research too, so you know how many unit has been built and how many are in queue.
   

Hi again everyone, I've stumbled across another obstacle XD. Anyway, how do I get the composition of units in a wave? Many thanks again XD.

Thanks again for your prompt reply, but unfortunately that is not something I'm seeking for  .

I'm sorry for not making this clear in the first place, what I wanted is the composition of units in different waves, (e.g. what units are in the divert1 wave and what kind of units are in the divert2 wave). I know there are ways to keep track of the units by manually adding units to a specific wave by creating one or more, but what if I wanted to know the composition of units in my enemies wave'? Is there a function or custom function to do so?

On top of that, how do I make a count of units that I'm currently engaged in battle for a specific wave? I can do a count of units, but that would compose of the units that I've counted earlier if they are not dead already, so that would exaggerate the count. Is there some kind of function which does a count of units for a specific wave which falls within its radius of sight?