Well, let's face it, you're not going to want to hang around in the cities. With everybody dead, all inhabited areas are quickly going to be infiltrated with the stench of rotting corpses. From a practical point of view then, the first thing to do would be to steal a car.

Then I would gather up all the basic tools and supplies I need to live, and a whole bunch of seeds (fruit seeds, vegetable seeds, and of course cannabis seeds), and I would raid houses and police stations for weed until I had a shitload. I would also raid supermarkets for food, especially canned food. Lots of food.

Then I would find a house to live in somewhere far enough from a city to not stink of rotting corpse but close enough that I could return for supplies if I had to. Preferably in a climate where you can still harvest plants in the winter. I would grow my own weed and try to start growing my own food.

I'm a pretty solitary person, but I think I would eventually go crazy with no human contact and the constant depressing reminder that I am the last specimen of Homo sapiens that there will ever be. I might commit suicide, or I might learn to cope with it. I don't know and I'm glad I don't.