Preloaders

I used a tutorial to preloading swf files. The tutorial I used was from actionscript.org and on it, the preloader was developed over the first three frames and then on the third frame the content was loaded in. I was told that this was old syntax, what gives?

Do i have a seperate swf file as a preloader and load the swf file over this?

If so how is this done?

Many thanks in advance