First Impressions
They can’t be reversed. Humility is always an excellent quality, however aim to represent yourself with an authentic level of confidence and curiosity.
Dress Code
The way that you dress matters, even when the dress code is non-existent where you work (as they often are for tech companies). People will always judge you based on your appearance, no exceptions, and that’s a fact of life. See the ‘Halo Effect’.
Furthermore, dressing in professional clothes reinforces your identity as a professional to yourself and others, and you will tend to conduct yourself in a way that is congruent with this identity.
Contradictions
Personality/appearance contrasts are polarising and inexplicably magnetic.