I agree with aquataholic's list, the only thing Id change is I believe IT and NTT are more commonly seen then AT. But that may just be for my area.
I personaly believe the tail markings do have alot to do with the IDing. True there are exceptions for almost every rule but for the most part ST will have 2 bars and IT will have 3 on the tail.
I also have seen ST's with 3 bars, I do not believe I have see an indo with 2 bars though.
I have noticed alot of people lately calling fish I would consider IT's, widebars. It's almost as if they want it to be a ST so bad, that if their IT shows any characteristic that are in any way questionable they automaticaly assume they have a Pulcher. They seem to totaly forget that Indos have the most varying traits.
Anyway, tail bars WILL help with IDing, but just like any visual aid used for IDing, it isn't 100%, but that doesn't mean it shouldnt be used.