An impostor player who stands out is bound to arouse suspicion. So instead of wandering around obviously following potential victims, impostor players are recommended to look like they are completing tasks. Travel to and stand by computers, the engine, etc. Other crewmates will be doing something similar, so it's not like an impostor will be inconvenienced by playing along. But pretending to complete tasks will just make it that much harder for the crewmates to identify the player as an impostor
Another important aspect of not looking suspicious is to engage in the discussion when a dead body is found. In that short discussion period before the expulsion vote, the impostor needs to act like they are another crewmate who is trying to win the game like everyone else.
While an impostor could lie and blame an innocent crewmate, this is not advised since the crewmates as a whole were likely spread all over the map. This means any crewmate the impostor blames could potentially have an alibi if another crewmate happened to be in the same area as them. Similarly, remaining completely silent is only going to cause nothing but suspicion. This means the impostor’s best discussion tactic is to act clueless. Ask questions, try determining who was where, etc. And when the group thinks they know who the impostor is? Agree with them. Even if it is another impostor. Trying to prove otherwise will only make the other impostor player stand out.