Smiling can be learned. If you don't like your smile, find out why. Maybe you need your teeth fixed or to wear lip gloss. Smiling pays big dividends, and you have to suffer the consequences of not smiling. To be magnetic is literally to draw people toward you.
Smiles attract others and therefore contribute to magnetism.
See chapters 4 and 9. An extraverbal technique is another name for nonverbal communication. You mention flattery as a factor in personal magnetism. Often these are hard-headed, somber, very technical people. An occasional person thinks he or she is so great that flattery isn't necessary.