When visiting the Jasna Gora monastery, men and women must dress somewhat conservatively if they want to enter the Chapel of the Virgin to see the Black Madonna. Specifically, shorts are forbidden, and women must cover their shoulders and navels. Paraphrasing our tourguide - "This is a church, not the beach".
In a place like Czestochowa, where you get lots of pilgrims and tourists, there are people who try to make their living of using your good will or naivety.
They may be giving you little hanger-medals, pins, or little pictures, and when you're just about to thank them, they tell you how much you're supposed to pay them. This is all too common in some seasons of the year. Just say firmly "Nie, dziekuje" (pron: "Ni-eh, genkooyeh") as you see them approach you or reach out to you. They usually withdraw... You can buy such things at the sanctuary.
By the way, this means "No, thank you" :-)
Tipping is now common in restaurants and service has improved greatly over the last few years. 10-15% is an average estimate, if your service is good.
BUT, and this is the warning, when you hand over your money to the waiter/waitress, DO NOT SAY THANK YOU. If you do, you are implying that they should keep the change, and they do. My son was stung like this when he gave a 100z³ note for a 26z³ bill. And the waitress was far too attractive for him to lose his cool by asking for the rest.
So wait until your change arrives, then say thank you and leave your tip.
on major days of pilgrimage, an awful lot of people visit Chzestochowa.
An all-time-record was the 4th World Youth Day in August 1991 when 1.5 million young people attended.