Generally call. If raised from BB call up to 3x. Then it's all about the flop. You can also fold to represent you are a stealer from the button, but in MTT online most player don't pay attention to other players behaviors, just their own stack, style and hand.
That is just completely not true, how can you say MTT players do not pay attention to other players, throughout the game you HAVE to look at your players to discover weak points in there game that you can use to your favour, for instance is Player A calling too often then folding if missed (we can use)
will he let go of draws (we can use)
is he limping and playing passively (we can use)
is he agressive (we can use for post flop play)
is he stealing too often (we can use when we have a restealing size stack)
can he let go of a steal attempt (we can use to know what to resteal with)
Pots shouldn't get to showdown too often with a medium stack, because your not playing your cards, your growing your stack through the players mistakes, by there actions they reveal what they most likely hold