The most influential designers I've worked with weren't always the most senior by title. They were the ones who consistently did a few things that built disproportionate trust: they were right more often than they were wrong, they were generous with their expertise, and they made the people around them better.
Being Right Is a Practice
Building credibility through accurate judgment requires being willing to make specific predictions and track them. "I think this flow will confuse users at this step" — then usability testing that proves or disproves it. When you're right, your next prediction carries more weight. When you're wrong, you demonstrate intellectual honesty by updating your view.
Making Others Better
The highest-leverage activity for a senior IC is raising the quality floor of the people around them. Thoughtful design reviews, unsolicited sharing of resources, pair-designing on hard problems. This is how you create organizational impact that scales beyond your own output.
Earning the Room
Influence without authority is earned through demonstrated value, not asserted. The designer who shows up to every cross-functional meeting with a point of view that's backed by evidence and delivered with appropriate confidence gets invited into more rooms over time. The one who shows up without preparation loses ground steadily.