My wife and I have been playing the earworm game for 34 years. For me, the best time to attack is early morning, before she is completely awake. I start by humming something, quietly, while we are still in bed. Just bits and pieces of it, never the whole tune. Then I gradually put all the pieces together, as we go through our morning routine, finally singing it out loud. At that point she is toast.
I find that I am most susceptible when I am intently focused on something else. especially if I am writing code or doing complex equations. She also recently discovered that she can get her best results while we are in the pattern to land. I get so focused I don't even hear her. Then, as soon as the plane is shut down I'll start humming whatever song she was humming in the plane.
Evil. Pure evil.