I would find a third party 'munitions factory. Not a government facility, but maybe a used gun dealer. I'd load up on as much ammo as I could.
Once I secure weapons, water filters would be next. I would need to have a large stock of light weight water filtration equipment.
I'd want to hole up in a facility which could give me advanced sight, perhaps on a hill, but be fairly immune to gunfire. Maybe a natural cave with limited entrances. I could set up enough fletchette / low yield claymore mines to protect the primary openings.
Caves are far enough down water often congregates in them. They offer some small protection from a/b/g waves. If the water could be filtered, it would offer a safe place to live. It's also fairly consistently temperate year-round.
From there, it'd just be camo gear and food.