We live in a port city thus see a lot of crew shopping. They are provided a crew bus where a certain portion of crew get a few hours off on that day. Sometimes a bit more IF the ship is staying overnight.
What I see....The bus makes the same tour every hour. Walmart/BJs/ Mall... where there is a special crew area with phones/banking/WiFi. Beach stop and back to the ship.
Walmart...Clothes & personal items
BJs....Cart packed with "Junk food" & personal items plus looking at their list from others.
BJs...Electronics/Games/ Lots in that department.
Mall...Clothes but mostly at the the crew area where they send money home and use the phones/WiFi and whatever else.
Beach to pick up those who decided that use.
I see the local fisheries at the wharf where there are about 5 or 6 Asians sent for FRESH local caught that a:m raw fish...For themselves.
I may see a few at something like Chick-fil-a....Some places they want to eat that is different.
Personally, I write a note for that special someone who made my cruise and was thanked profusely so it must be something they appreciate. I don't ask. A few hunted me down and one was sending it to his Mother, he was so proud he was appreciated.
THAT cruise 'Appreciation Comment Card" that are put out by the ship IS important....TO them... Point out that special person....Fill it OUT!
Have been asked only about silly head gear at holiday time which I give them.
Otherwise the short answer is...Manners...And "THAT written Comment Card" along with a "Hand written personal "Thank You" in an envelope with Cash MONEY!