Facial features as an indicator of personality
The "good" characters in Lucky Jim are fairly easily distinguished from the "bad" characters, and one way this distinction is made is through the relative mobility or immobility of their features. Characters like Professor Welch, Bertrand, and Margaret have almost static faces—if their expressions move, they move slowly, and do not change the general quality of their facial structures. On the other hand, Dixon spends several minutes trying to think back to the many variations of Christine's face. Dixon's own face is mobile and we see that characters that Dixon trusts, such as Atkinson and Gore-Urquhart, have animated faces, or at least several faces that they use to convey emotion. Thus it seems that the characters who have less to hide, and who are more genuine with Dixon, have mobile faces that convey what they're thinking.
A capacity for contempt as a marker of male "soundness"
All three positive male characters—Bill Atkinson, Dixon himself, and Gore- Urquhart—share a decisiveness about what they do and don't like. Bill Atkinson is remarkable perhaps only for the power of his contempt. Dixon, too, is able to get out of his oppressive situation with Professor Welch and Margaret because he sticks to his instincts, dividing the world into people he likes and those he does not. At the end of the novel, Dixon and Gore-Urquhart bond over their shared contempt for social functions, and Dixon's ability to express contempt seems to be what gets him a job as Gore-Urquhart's assistant at the end of the novel.