I'd say "This lecture will be fascinating, so get your tickets before they disappear!", but do not quote me on that.
The first option (<span>He was casting quick, sideways glances in the direction the bus should be coming from, and his left foot beat a steady rhythm on the hot pavement) is the best because it directly gives examples of actions the man is doing. The other three examples are much more vague. They refer to his "actions and mannerisms", "behaviors", and appearance rather than specifically stating what those actions and behaviors are. If the author added the first sentence, which refers to specific motions of casting sideways glances and tapping his foot, the reader would be able to create a much more detailed image in their mind.</span>