First: start early, at morning's first light.
Second: pace yourself.
Third: be well-hydrated.
As well, I would suggest that, on day one, proceeding out of Leon 6 km out, hang left at Virgen del Camino and proceed through Fresno and take your first night at Villar de Mazarife. Walking along the Leon road through Villadangos is not the most pleasant experience.
As far as being alone, you will not remain alone for long. It is likely that you will find yourself in the company of other pilgrims, making some incredible friends as you go along.