You can either follow the links on the intro to player 10 or I will present all the links here. To get started you need to install the Flash Player 10 from the Adobe website. If it was successful you should see above a rotating textfield. In order to develop for player 10 you need to use the Flex 3 SDK or you can use Flex 3 if you have it, since there is currently no support in Flash CS3. You can download the Flex 3 SDK here. You need a nightly build of the SDK dated after May 15. Place it on the desktop. Now you need to make some changes in the file in the folder frameworks - flex-config.xml. This is described on a Adobe page. There is, however, one change, which I found out after a long search and not described there. It can happen that you cannot load any textfiles and when you test using try and catch you will get a security error #2148. To avoid this open again the flex-config.xml and change "true" in the following line: <use-network>true</use-network> to "false". Now the error should disappear. You are now ready to write your first script for player 10. I will present the script for the above movie.

We place an empty .as file in the flex_sdk_3 folder. Name the file "Start.as". Open the file using a texteditor or as I usually do using Flash CS3. The file is very similar to a regular AS3 file with a few additions.

NOTE: it is important to add return type of a function also if void or there will be an error.

package 
{
	import flash.display.*;
	import flash.events.*;
	import flash.text.TextField;
/*
/ Setting the movie parameters.
*/
	[SWF(width="400",height="400",backgroundColor="0xF1F5F9", frameRate="24")]
	public class Start extends Sprite
	{
		private var bitmap:TextField;
		public function Start ():void
		{
/*
/ We create a textfield and position it.
*/
			bitmap=new TextField;
			bitmap.mouseEnabled=false;
			bitmap.multiline=true;
			bitmap.autoSize="left";
			bitmap.x=175;
			bitmap.y=200;
			addChild(bitmap);
			bitmap.text="You have installed Flash Player 10.\n";
/* 
/ We add an eventlistener to have continous rotations.
*/
			addEventListener (Event.ENTER_FRAME,downHandler);
		}
		private function downHandler (event:Event):void
		{
/*
/ We add new AS for rotating in all directions.
*/
			bitmap.rotationX+= 5;
			bitmap.rotationY+= 1;
			bitmap.rotationZ+= 3;
		}
	}
}

Instructions for Flex-SDK users

This is not required if you have Flash CS4. Once you wrote your script you want to compile it. I describe the procedure for the Mac but for PC it should be similar. Open the Terminal window and enter this code:
cd Desktop/flex_SDK_3/bin/
then press return. Then enter this code followed by the name of the class file:
./mxmlc ../Filename.as
Then press return and the script will be compiled. Any errors will be shown. And this concludes this tutorial.

Senocular's tutorial about player 10 drawing API.