When I was trying to find out how to get from Krakow to Auschwitz recently, I had a difficult time trying to get information from the people at the hostel and tourist information. They all wanted me to go on a tour to Auschwitz.
I wanted to go alone and in some way, experience the journey there without the noise of a group tour. By all means if you want to go by tour and do not have much time, go by tour but for everyone else, the following is the easiest way to Auschwitz;
Train to Auschwitz or Bus?
Some people might want to go by train to experience the rail journey taken by the prisoners, as morbid as that sounds. Anyway, do you have to book tickets for the train to Auschwitz? No, you can just show up and buy one.
It takes 1 hour 30 minutes but I would suggest going to the central station early so you have time and room for error when finding the right desk.
However, I recommend you go by bus because they drop you right outside the Museum OR at the train station, if you are staying in Oswiecim. The bus takes 1 hour 30 minutes also.
Hotel in Oswiecim
There is not a lot online for hotels etc but if you check out Booking.com you will find a few reasonably cheap options in the centre of town. I stayed in the Home Traveller Hostel (Old Tree Villa Hotel is next to it) which I liked but it is a walk from the town of approx 2km. I did not mind the walk each day.
You are probably best to reserve a place on Auschwitz.org which does not cost any money and neither does the entrance. I did not reserve and there was no problems getting inside.
If you have a bag, you will need to leave it on the tour bus or in the luggage storage at the entrance (kiosk to the right of the entrance).
Your time is unlimited from what I can tell and there are plaques all around the camp to explain what you are looking at.
A free shuttle bus will take you to and from Birkenau which is 4km away.
Warning, it is a very emotional place to visit.
Should you take a tour of Auschwitz?
In my opinion no, the groups look very rushed and miss out on a lot. However, the guides do explain everything brilliantly.