I don't play it often, but I do play it. I'd rank it as my 3rd favourite after Tag and Tekken 5.
I have dabbled with pretty much every character but always find myself coming back to Hwoarang and Xiaoyu. Both are quite complex so it's hard to come up with any quick summary for either of them. At the most basic level, though, what works for everyone else in Tekken works for them too.
First, learn ranges and spacing, and develop some sense of frames. Tekken is almost exclusively about punishing mistakes and the easiest way to punish something is to avoid the hit completely. Know what your opponents big moves are and work at a range where they are neutralized (either by being to far away to hit or by being too close to execute for fear of a counter hit). Similarly, learn your own moves and where/when they work best. Hwoarang, for example, fights best at a medium range. Even his fastest kicks get stuffed far too often if he's too close, and he only has decent long range attacks but little long range mix up potential. At the right range, however, his kicks can stuff most of what an opponent can do and the mind games created by his stance switching have enough time/space to work. As far as frames go, if you ever get really good at the game you'll have to know at least a little bit about frame data. It's not something you need to memorize top to bottom, but knowing each characters fastest and most common moves will help open up your own game.
Second, learn some combos. Tekken may be famous for it's long juggles but the biggest thing to know is really just something you can do consistently and, especially in T6, what to do at the wall. A 5 hit combo for 40% damage that you never mess up is better than a 10 hit combo for 75% that you mess up a lot and that gets interrupted by wall contact most of the times you don't mess it up.
Third, learn your moves.. and don't use most of them. Tekken has a lot of moves but once you become familiar with your character you'll quickly realize that many of them are either very situational or are simply worse variations of something better. Don't feel you need to somehow use everything on your characters move list and really don't worry if you can't master the 10 strings. 10 strings are near useless in real play.
Finally, learn how to be patient. Tekken is a game of extremely high powered offense. That just means you need to be careful. Sure you might get lucky bulldogging someone, and rushdown can work if you really know your character, but one little mistake really can cost you the all important momentum. A second mistake will in most cases cost you the entire round. Constant offence in Tekken isn't a bad thing, just make sure it's done in a smart way that is luring your opponent into making a mistake instead of just fishing for a lucky hit of your own.