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know your characters…learn their strengths & weaknesses
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know their move properties
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know their combos…this is important…because a strong offense is one of the key factors to win(e.g being able to do massive damage each time the opportunity arrives)
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know the fundamentals.
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get a lot of experience…
And here’s what Yuu(famous Feng player) said when he was asked how to be as good as him…
“first play with weaker or players with same skills as you…to build your confidence. Then play with better ones. Also make sure you can do your combos consistently”.
I rarely play online Tekken…but I’m sure playing online will certainly give you experience, learn how to play against other chars. You’ll probably face ‘cheap online tactics’, there are not used in offline play…because there’s quite a big difference in playing online & offline…But at least you’ll learn more about the game.
Btw Bogus Journeys shows how offline players deal with the online netcode…
[SIZE=4]Bogus Journeys - Season 1[/SIZE]
there are more technical combos… such as ones that require stance transitions…and there are a shit load of them in Tekken…
such as DSS cancels…DCK~WS+1,2…RLX~HSP, and so on.
but basically many combos in this game are pretty easy to learn…
that’s why the newcomers I’ve met…can do combos and do a lot of damage consistently…but they lack the fundamentals and knowledge of their characters.
then you’ll most likely enjoy TTT2… 
the basic movement in this game(backdash, side step, side walk, running ,etc) …is explained in either Tekken 101 guide, or the 1st episode of Level Up Your Game…IIRC
As you play & learn more of the game you’ll learn more advanced movement related techniques.
Such as back dash cancels, ESS(electric side step), Hayashida Step, Fox Step, Wave Dash, Light Dash, Snake Dash, etc.