What would you do if you were alone in the world?

1) Safety.

Several days is fine, but the nature will start taking over. Predators, unfiltered water, etc.

I would spend several hours a day for the first few weeks to get access to ammunition and weapons and learn how to use them.

2) Shelter.

Protect my place as well.

Maybe find a better place than my current location. Where it is safer, food is easier accessible, fire can be made, etc.

Again, not too urgent, but with no humans around variety and likelihood of accidents increase.

3) Food.

Plan A: Stock up on what doesn't get bad for several years.
Plan B: More healthy and sustainable options.

Gas-based fridge and a large supply of gas can store plenty of juices or even veggies.

4) Health.

Come up with a plan w/o professional healthcare.
Stay fit. Exercise. Don't burn yourself.

5) Scale.

All of the above can be scaled quite well. I would probably dedicate some time around the 2nd month to have better reserves.

6) Technology.

Electricity? Gas? Cars? Boats/airplanes I can use?

Computers? Connectivity?

7) Personal growth.

Reading and research, at very least.
Building something I feel important.

8) Plan.

If I assume that humans will appear somehow, I will need to prepare for it.
Depending on how did this happen, I will estimate the probability of whether there are more people and their potential locations.

Perhaps remote islands. Perhaps from the international space station.

If no, I will look for other means to continue with the humanity. Had I been a girl, sperm banks may have helped. Guy's life would be harder, but I would at least dedicate some time to do my research and try to figure out if there are feasible options. I have heard of people freezing themselves in hopes to be resurrected. This is probably not something I could succeed in, but perhaps fertilization is still possible.