Think of the areas of the structure and divide between areas heated/air conditioned and those that are not. Think of the spaces you want to heat or air condition; this is the “conditioned air space” you are paying for.
Look for cracks, holes, pipes, etc. that enter the “conditioned air space” area. These should be sealed to save energy (and keep pests out).
If there is an attic, check the depth of insulation installed. The hardware store sales associate should give you the average for your area.
In the attic, if the insulation is pink, look at any areas around pipes, chimney, light fixtures, or wiring. If insulation is dirty, “conditioned air” air is escaping.
If there is any type of door to the attic, make sure there is insulation covering the door when closed to prevent loss of “conditioned air.”
The advantage of a full energy audit’s detailed information is to develop a plan and budget to make those changes to save the most money.