If you are experiencing “cold spots” in your home, first make sure there are no obstructions that are blocking the vents such as drapes or furniture. This will improve air flow.
In many homes, there are often spots that just don’t seem to heat properly. In a lot of cases it is a fairly easy problem to remedy.
Most cold spots are due to inadequate air circulation. Furniture can be blocking the circulation patterns of a room. Consider where the bed, sofa or other furniture is located in relation to where the air vents are located. Moving a large piece of furniture just a few inches to allow more air circulation can make all the difference. Air will take the path of least resistance, so if there are any obstructions to the air flow entering the room it will tend to bypass that point and continue elsewhere.
Also consider locating a small fan near warm air outlet vents, it can direct the warm air across a room instead of straight up to the ceiling.