If I want to fly from city A to B, but want the flight to stop in city C (A-C-B), how do I search for that?

Say I want to fly from Lubbock, TX to Seattle, WA or Portland, OR or somewhere in that area, but I want to stop in Reno, NV to visit a friend during a stop/connection. Is there a way to search flights based on stops/connections? If that particular connection isn't possible, how about Atlanta to the west coast with a stop in Reno? Thanks!