lol, well if you guys ever read the comic (which is pretty cool actually =D ) I guess I'd better throw in a few terms and notes...
Triple A: you only get this if every step is a perfect, no fluff up, nothing wrong at all; every step is placed with almost machine-like timing for THE ENTIRE SONG. Scary stuff but something to aim for I guess o.O
Perfects and Greats: When you step there's several ratings you can get for each step based on how on-time you were... perfect is the absolute, outside of special play modes this is the highest you can get. Greats are next best, they're the lowest that most people are happy with but if you're playing hardcore you still try and keep them to a minimum... there's also 'good' and 'boo' which means you kinda just skiffed the arrow, barely catching it and then there's plain old miss =3
Max 300: the 'max' tunes are generally credited with being some of the nastiest tunes on there, though 'japan' and 'tsugari' are supposedly feet-breaking tunes too. Course, different songs revolve around different styles so it depends on what you're good and bad at... plus it helps if you actually enjoy the tune ^~
~pokes dubb~ chances are if you're watching them then you want a go too =D
edit: games are about fun, I think it's kinda sad so many people miss out on stuff like this just because they're afraid of how they'll look or they won't match up to other people who're playing on it. Sometimes you get some jerks impatient for their turn making comments (only one I've had so far is someone asking why I use my arms while I was in the middle of a tune but I just pondered aloud why they ask stupid questions and they shut the heck up XD ). DDR won't help you dance or anything but it's a good giggle and it keeps you in shape; if games were as active as this normally you'd see a lot more healthy looking gamers :p