1. Arm yourself. In all probability you are not alone. Handguns for now.
2. Look around, cautiously. Do the best you can to determine what kind of empty world you are in… don’t yell to find other people until you know you want to meet them. They might be zombies, mutants, alien zookeepers, etc. Ask yourself some basic questions: Are the animate dead walking the street and hungering for living flesh? What do you smell? rot? decay? Is the hideous shambling form you spot in the distance a horrible mutated survivor or the undead? Will the mutants hate you for your good looks or blame you for destroying the bulk of humanity? Will the alien zookeepers bring you a mate? Will she be hot? It will take at least one act before you know for sure what’s going on, so stay flexible in the first few days.
3. Get some wheels. A motorcycle will get you through all the wrecked and abandoned but you have to worry about wrecking it (no doctors) and it really can’t carry much in the way of ammunition and supplies. A rugged off-road vehicle with simple mechanics would be best, but nothing with an open top (zombies.) Take spare tires and basic vehicle fluids and parts and equipment (battery, spark plugs, distributor cap, etc.) Fill up as many gasoline cans as practical before the power goes off. Getting gas out of underground tanks is not as easy as it looks in the movies and siphoning gas out of other cars is time consuming and leaves you exposed (zombies.)
4. Hit the grocery store. Stock up on canned goods, can openers and calorie-dense foods with a reasonably long shelf life such as nuts, chocolate, and dried fruits. Eat all you want… your weight will never be a problem again. (If there is a last woman, she’ll accept you for who you are.) Bottled water, medications, hygiene products are also on the shopping list, but don’t try to get everything, this is all just to tide you over until you…
5. Get out of the city. Hundreds of tiny events out of your control can go wrong in a city and kill you: fires, disease, roving gangs of mutants, etc. You want to think fortress. Find a little place in the country and clear the trees around it for a free-fire zone. Stock up on firewood and candles. Keep a generator going if you must, but ease back on it so that when it breaks or there’s no more gas, it won’t come as such a shock. Make trips back to urban centers to stock up on food, medicine, and to hunt for the last woman on Earth (unless you already found her… but would a spare really hurt?) Stockpile, stockpile, stockpile. Food, weapons, ammunition, medicine, pornography, clothing, fire extinguishers, how-to books and tools. Take up farming. And if any lived, get a dog.