In San Francisco, you just call the city. They'll give you a few bottles to fill, which they will test. I remember that they even came by personally to either deliver or get them. (Or both?)

It's easy to determine if pipes are made of lead if you can access the pipes. It's less easy to determine if they have some residual lead from upstream pipes that's settled into the corrosion layer on the inside of the pipe (and could be released later)

There are testing services and test strips available for testing your water, which works even if you can't access all the pipes on the way between your source and your sink. A testing service will likely check for a list of contaminants and not simply lead, and most likely have better accuracy and precision than test strips you use yourself.

My county water district publishes the monthly report of detected levels of all of the regulated items: https://www.valleywater.org/your-water/water-quality/water-q...

They also say that lead is rarely injected into the water supply from the water supplier or water mains, but usually much closer to the home (eg. “Goosenecks”).