Install a digital thermostat they are more efficient.
Insulate inside of cabinets: use Reflectix and ridged foam.
Insulate inside your basement: use Reflectix and ridged foam.
Use Reflectix on the windows if you don't have storm windows.
Use thermo blinds or curtains.
If the sun is not shining through the window close the curtains or blinds.
In stall a vent free propane heater, they use less propane and no electricity, they can cause condensation though, so circulate some air while using it and only use them during the day.
Install a window shrink film kit on the screen door
Park with the side of the trailer with the most windows facing the sun if possible.
Use vent hatch covers.
Insulate the hot water heater and pipes.
Cover the microwave vent to cut the draft and don't use it.
Cook with the oven when possible then leave the door open and let the heat out as it cools.