Action script version
Most importantly you need a pre loader you can download a newgrounds preloader if you dont have one.
I think you should specify that this is AS2 and not AS3 because with AS3 you cannot apply actions directly to a symbols.
The tutorial I think could use more detail about making movie clips with animated characters like walking cycles and then explain how to swap movie clips with code like changing the idle standing pose to a movie clip with the walking cycle when hitting the arrow keys, then changing that to a jumping pose when in the air.
Overall I think it needs more planning tutorials are not easy to make and like any artist that storyboards for a game or animation you need to create a lesson plan and go into more detail, perhaps create separate tutorials for Platform and 2 player. Again specification for new flash users what action script version you are using becuz new flash are probably using Flash CS3 and up and will have problems using AS2 on movie clips.