Step one
Find every person who represents you.
From your two senators down to your school board trustee. A ZIP code is not enough, because ZIP codes cross district lines.
How this works
Your address is matched against the Census geocoder to work out which districts you live in. Those districts decide who represents you: one congressional district, a state senate and state house district, and the county, city and school district boundaries around your home.
A ZIP code alone is not enough. ZIP codes cross district lines, so two neighbours on the same street can have different representatives. That is why the full street address is needed.
Want to understand the offices themselves? Read the guide, or go straight to writing to them.