Hotels
Choose a hotel for convenience and short-term stays
https://niebieski.com.pl/
Apartments to Rent
Booking.com-best site to find apartments
Choose an apartment for best deals and added benefit of washer or kitchen
Try to stay less than 1 mile from Main Square when booking
Sample bookings:
Booking.com: St Agnes Apartments Old Town
Swietej Agnieszki 3/ 1A,2A,3A, Old Town, 31-071 Krakow, Poland
App to plan travel using public transportation. Tells you which lines to take, what time they arrive etc.
Make sure to set your location to Krakow before testing.
For discount flights to see multiple countries:
https://www.ryanair.com/us/en/
https://www.flypgs.com/en
https://wizzair.com/en-gb
Be aware that most have strict baggage rules. Consider alternate dates to get the best deals.
Random tips:
Do not rent a car in Krakow. There are several areas that cannot be accessed by car at all and roads are much more narrow. Uber is easy and cheap if a car is needed.
If planning to rent a car elsewhere, be sure to apply for an international driver's license ahead of time.
Adapters are needed for electronics. Here is a link to some from Amazon but any that say safe for Poland should be fine:
https://www.amazon.com/dp/B097GCZWMM?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1.