I love playing Neutral Killers. You are doomed most of the time, but it’s just such a great experience to play as.
Anyways, here are my theories on what you can do to win more.
General
As a Neutral Killer, you must survive. Unlike the Unseen or the Cult, you cannot afford to lose a single member. You are the only person on your team, and if you die you lose. So claiming is key.
Unfortunately there aren’t many good claims. In general, Knight and Court Wizard claims are distrusted, since they are common evil claims. I find that generally Sheriff or Paladin is a safer claim, since they are easy to fake, but less mistrusted. The problem is you have to know what faction is present, you generally have to look for signs of one of the factions. Luckily you can easily switch claims if you need to. Of course, if you are jailed night one, you can’t use this, without a 50/50 chance of being screwed.
Possessor
My favorite class by far. You have a unique advantage as Possessor, and that’s the fact your Puppet Strings can fake Maid Spy. Unfortunately, if you claim Noble and are asked to use Political Pressure, you are screwed. Luckily, I find most people don’t do that.
That’s not the only thing, though. Possess allows you to jump into the bodies of confirmed people, which means you don’t have to claim and are in a safe place. The downside, however is the fact that the Psychic will be told who you are, if you still live. So you should consider chain jumping, hoping to jump into the Psychic. Conveniently, this can also heal you of poison/bleeding.
You also don’t have to worry about Knights, as the Knight will kill who you are controlling. If you do this twice, you can even kill the Knight.
Do not possess the King, as your lack of the Royal Finger is glaringly obvious.
Reaper
Reaper lacks the advantages the Possessor has, but luckily he makes up for it.
Your souls are convenient for a couple reasons: One, you are immune to everything. You can’t die of poison, bleeding, or even a King’s execution (unless you run out).
In addition, they can be used to power useful abilities. Chill can lock away information, although it confirms your existence and gives them access to the dead. Still, it’s also useful to avoid getting executed, as it stops votes as well. It does not stop day abilities, however, like the Royal Finger.
Gather Darkness can help you take out the King or the Mastermind.
Reaping also delays information getting out, so it’s great to use on investigators.
Sorcerer
Remember, the Unseen/Cult is your friend. If you ever get poisoned or bled by them, do not mention it, as it can signal them who you really are.
If you want to take this a step further, draft your death note like this.
Assassin, you poisoned me day three. I am the Sorcerer, so contact me.
Always kill the Inquisitor. They are your biggest enemy, and if you kill them, you are stronger than any other Neutral Killer, as you have their powers with the Unseen/Cult on your side. The extra night it takes to kill them is well worth the cost.
Use Magic Circle on confirmed Blue Dragon, such as the Prince, as this can clear out pesky protectors such as the Physician and Knight.
Psycho King
If you managed to crown yourself, the Blue Dragon trust you and you can run rampant. No advice needed here.