I try to role play properly while playing AC2, trying to be as much like a proper assassing as possible. Always stealthy, never attracting attention, most of the time not even letting the target see me. If a kill is unnecessary, I try not to do it.
I mostly stick to the streets and blend unless it's impossible to access my destination by the streets, in which case I access the rooftops via a secluded alleyway a few streets away.
whilst on rooftops I try to avoid archers. If that is proven to be impossible, I either assassinate them quickly and make sure their body doesn't drop to the streets below, or I full out duel them with my knife.
I use the hidden gun only if I want to attract attention during a kill(as if the assassin is delivering a public message by killing the target) and I always use smoke bombs to escape. My weapon of choice is the poison blade, or the hidden blade, and I use the sword only in rather big fights.
Yeah, I have a few pretty cool kills.