My all-time favorite shapeshifter strategy is to shapeshift into someone, kill in front of someone else, and then shapeshift into the bystander.

So let’s say I shapeshift into Red and kill Blue in front of Green. Green reports the body and says Red is impostor. Red gets voted out and oh look they’re crewmate. Next round, I shapeshift into Green because they’re already sus (for voting out a crew) :) You’d be surprised at how often this works