The fastest non-specific method to determine the QRS axis is to find the major direction of the QRS complex — positive or negative — in leads I and aVF. If the QRS complex is upright (positive ...

See the ECG basics section on determining axis for details. If the QRS is upright in lead I and downward (negative) in lead aVF, then the axis is between 0 and -90 degrees, likely left axis deviation.