Identify the area of the attic where the sound of movement and squealing is coming from before entering the attic. The squirrel will probably stop moving and making noise after it detects your presence in the attic. So go directly to the area of the attic where you notice the noise coming from.
Turn off all light sources in the attic. Look around quickly for any light penetrating through holes in the attic. This hole may have been created by the squirrel and is being used by her to access the attic.
Turn on your flashlight and walk over to any areas where you notice holes to look for the squirrel.
Walk around the exterior of the attic and look into the soffit screens. Squirrels often gain access to the attic through the soffits, and the animal may still be near its entry point.
Look for squirrel waste in the attic. The squirrel often won't stay near this mess, but it is an indication of where it travels.
Stay still, quiet and turn off the light. Listen carefully for any movement. You may need to sit still for 15 to 20 minutes before the squirrel believes you're gone and begins to move about. Then follow the sounds.
Follow the stench of a dead carcass, if you believe the squirrel is dead. With gloves on, remove any boxes and insulation near the stench to uncover the carcass, if needed.