What are some common troubleshooting steps for a gas furnace that is not heating properly?

Some common troubleshooting steps for a gas furnace that is not heating properly include checking the thermostat settings, ensuring the gas supply is on, inspecting the air filter for blockages, and examining the pilot light or ignition system for issues. Additionally, checking the ductwork for blockages and ensuring the furnace is receiving power are important steps in diagnosing the problem.