I'll ignore One Night Werewolf for now and focus on Avalon and more typical mafia games. To begin with, something that you may be overthinking:
Not everyone is expected to bluff or lie.
For the basic villager or knight, there's no harm in being wholly open and honest. You want people to believe you are a villager which is true. You aren't privy to any information that you don't want people to know (the one thing you're sure of is that you're a good guy). Be open and honest about suspicions. Choose succeed for every mission. Worst case scenario, you make an honest mistake.
So when does someone lie?
First, when they're the bad guys. The bad guys definitely don't want anyone to know their role since if people knew they'd be killed (werewolf) or never taken on missions. This means pretending to be a good guy.
This is where the bluffing comes in. Minions know the identity of minions. Now, you probably* don't want to out your fellow minion and you definitely don't want to out yourself. This means any "suspicions" you have will be lies to draw attention away from you.
Second, when you're powerful. Merlin, for example, knows the identities of all the minions, but his team loses the game if he is identified. This means a difficult balance between using that information and remaining hidden. I won't go into detail here- there's at least one question that covers this specific case.