This advice is something I would give myself if I could time travel back to December 31st, 2009, when I was still allowed to buy new things.
I would advise me not to go shopping for a year's supply of bras and underwear 15 minutes before the store is closing on New Year's Eve. You don't get a chance to try on the bras (always a bad idea because everyone knows you need to try on at least a dozen to get one that fits you right).
Also with just 15 minutes of frenzied shopping time, you don't look very closely at your other purchases, which means I have 18 pairs of new underwear that make the 'navel knockers' my grandmother used to send me for birthdays look positively scandalous.
At least I got the socks right. Only 332 days to go.