From this presentation.
Strategies for Villagers:
Kill quiet people.
Rubyists know this as the Marcel Utility Index, but it's known outside the community as well. Quiet people are dangerous. Being unobserved is great for a werewolf. A villager who doesn't express their opinion doesn't give you any information except their vote, and you need information. If somebody isn't providing that information, they aren't helping the village survive. A quiet player is either useless or a werewolf, so killing them is a good decision either way. This is especially true in the early rounds, when the information available is pretty scant.
Because you don't want to get killed, and because you need to get information circulating to find out who later contradicts themselves.
Watch turn-to-turn alliances, voting, and accusations
These are your tells.
Watch people when they get their cards at the start of the game
This is a tell too. Nine times out of ten, if somebody doesn't get a werewolf card, there'll be a tiny flicker of disappointment. Seize on that.
Lynch all liars
The only in-game motive for contradicting yourself is if you're a Werewolf.
Don't waste the seer turn
Before the villagers go to sleep, they should recommend someone for the seer to find out about. This is true even before the seer is known, or when the seer's identity is in doubt (and the seer's identity is really always in doubt, until the seer dies). Don't make the seer do all the work, and don't leave it up to luck, either.
Analyze the situation for yourself
Even though it's important for the villagers to create consensus, that consensus can be manipulated, and will. You need to keep an independent mind.
Strategies for Werewolves:
Create confusion and dissent
Divide and conquer. The more confused players are, the more likely they won't figure out what's going on. As a werewolf, your best-case scenario is total chaos, with everyone mistrusting everyone. In that situation, the villagers' process is essentially random, and you have a very good chance of winning.
More than anything, this is key. However you acted in the last game, you have to act that way in the game where you're a werewolf.
Act like a villager
Make sure people see you accusing, and more importantly, weighing the evidence. The villagers know that if you don't have to think it over, you're a werewolf. Let them see you thinking it over.
Argue with your fellow werewolves
People keep a close eye out for factions. Anyone who automatically trusts another person is suspect. The only people who have enough knowledge to trust each other are the werewolves. (Or the seer, but the seer needs to hide their identity.) Correspondingly, if you're a werewolf, you want to seem like you don't have any trust in your fellow werewolves. If people notice you acting as a group, you'll all be hanging from the trees.
Lynch your fellow werewolf
This is a tried-and-true strategy, but it's also a dead giveaway if it's done wrong. You have to either be out to get your fellow werewolf from the beginning, or look as if you were rationally persuaded by another person's arguments. If you see another werewolf is basically caught, and you turn right around from trusting them to suspecting them, it can be obvious that you're abandoning them. The best thing is to appear mistrustful but reasonable, and transition slowly, at a judicious pace, to appearing certain they're a werewolf. Then when you vote to lynch them, the villagers will trust you.
Act like a novice
Novices freak out, panic, and lynch experienced players, who they absolutely need alive. Panic spirals out of control easily in groups, so it's not only easy to lynch innocent villagers and contradict yourself without getting caught if you appear panicked, it also encourages the kind of confusion and fear that helps you win the game. Appear to panic, and encourage panic in others.
Pretend to be a seer
The seer is a special asset, and no villager wants the seer dead. Act like you're the seer, and people will be more cautious about killing you. Actually say you're the seer, and you can really fuck with their heads. Either you lead them down a wild goose chase, killing innocent people, or you force the real seer to reveal themselves. Either way it's a werewolf win.
Not killing the seer
The idea is, nobody knows if the person who says they're the seer really is the seer. So if nobody kills the alleged seer, then they probably weren't really the seer, but rather a werewolf. That makes all their information worthless, because if nobody believes it, nobody will use it. If somebody comes forward as the seer, and their credibility is in doubt, letting them live can intensify the confusion and dissent that you need.
However, not killing the seer is an infinitely complicated strategy compared to the simpler version: killing the seer. If you're a werewolf, and you think you know who the seer is, and they haven't come forward yet, then killing the seer is a no-brainer. Likewise, if the seer comes forward and people trust them, kill the seer. You'd only want to let the seer live if their credibility was in doubt.
Strategies for Seers:
Understand the end game
This is the most important strategy for the seer. Basically, you want to stay alive, quietly gathering as much information as you can, until the group gets down to a certain size, and then come forward. The werewolves will kill you when you come forward - either immediately or soon after - but if you have good enough information, the villagers will win.
Check out experienced players early
Experienced players know what they're doing. An experienced werewolf is more dangerous, and an experienced villager is more useful. Novices act so randomly that finding out who they are doesn't help you right away. Experienced players also come up with good reasons for suspecting people, and if you know if they're werewolves or not, you know if the "reasons" are bluffs or not.
Check out nearby players, confide in them
If you check out a villager and know they're a villager, you can tell them what you know. Of course, at the same time, pretending to do this is a great strategy for a werewolf, so if you're a villager and this happens to you, keep in mind that all a whisper like this really means is that the other person isn't a villager. Anyway, as a strategy for seers, this is good because it allows your information to be shared; however, if people see you whispering to somebody, they'll think you're both werewolves. It's a bold strategy, but it's also a risky one.