People need to hold their tempers and expect queues in some places, with relaxed Covid-19 restrictions likely to bring shoppers out in droves.
The new traffic light system came into effect yesterday, and it has allowed cafes and other Auckland shops to properly open for the first time in months.
Retail NZ chief executive Greg Harford said he has heard of shoppers getting upset over staff checking vaccine passes.
"There will be perhaps some queues and limited numbers of people allowed into [some] stores.
"Please just be patient, everyone will get what they need in the end."
He said reports of customers getting angry with shop staff asking to see proof of vaccination were unacceptable.
"I have heard about some customers getting pretty grumpy when they're being asked to show their vaccine passes.
"My message to everyone is 'please stay calm, if you're asked for a vaccine pass be ready with it because it is a Government requirement'."
Harford said Covid-19 supply chain disruption meant there were shortages of certain products, so people should get out shopping this weekend if they want to secure particular items.
An Auckland mall owner is expecting a bumper shopping day.
Glenfield Mall co-owner Dallas Pendergrast said today would be busy, with Christmas shopping in full swing.
"We've got a lot of entertainment on, we've got Santa arriving today, so that will be a big drawcard for the kids."
Pendergrast said vaccine passes were not needed to enter the mall itself, but would be required in some shops.
Police taking education approach for now
The police will hold off on slapping people with fines for breaches of the Covid-19 traffic light rules, for now.
They say there will be a period of adjustment while the new system beds in, and they are focusing on educating people.
Covid-19 breaches can still be reported to the 105 phone line, and police will respond where property and safety are at risk.
Meanwhile, border checkpoints remain at Auckland's northern and southern boundaries until the middle of this month.