Ethics
Though Assassins is a sneaky, clever game, I feel there is a certain ethics component involved. While I do encourage you to use whatever you can to gain an advantage to make kills, keep a few things in mind:
1) As changed from the original rules, I DO NOT have a problem with you inviting your target into your room to make a kill. If you can create this situation, so be it.
2) When people are sleeping, it can get a bit tricky. If someone is sleeping in the afternoon and the door is open, by all means make your kill. But if it is 2 in the morning and their roommate leaves the door open slightly to go to the bathroom, and you go in, wake the person up, make your kill, and leave..I feel this kill is ethically questionable. Try to find a reasonable balance between these situations.
2a) For any kill in general, just think about if you would be really, really pissed (above and beyond any normal range pissed) if you were killed in such a manner, and use this as your guide.
3) Don't go around trying to find out extra information. If person A kills person B, person A should not be trying to find out everything person B knows.
3a) If you are dead, don't go talking about the game to others. Try to be fair to all those still hunting.
4) As far as the witness rule goes, just don't have people really close by if you make the kill in public (with no mask). People can be within a pretty wide range if you make the kill, just as long as they are not close enough to really see what is going on. Use your best judgment. Secrecy is key to survival.
5) Have a kickass time, and use good judgment...but do wacky stuff :-)
6) Check out the rules page again at Rules