Just a warning though, on the heirarchy of online netcodes IMO...
BB>VF5=Skullgirls>SFxT=SF4>MK=T6=KOF13>>>>KOF12
(Haven't tested SCV and MvC)
So you will get pretty frustrated playing online for the most part if you're not accustomed to the lag.
The only characters that are massively different in this iteration is Julia then followed Law, Zafina, Raven.
I believe Leo and Paul are the least changed.
And as for what to do once you played Tekken 6? Just have fun
. But ideally, I'd definitely say to familiarize yourself with the movement and wakeup options. And specifically for wakeup you have to play against human opponents to truly learn how how to get up from what situations.