1) Send out an email "I will be collecting" notice early on (not two days ago as in my son's class). Early like in the first week of December. It may seem a bit premature, but the extra time is precious.
2) Don't set a specific amount of money to collect from each family. Some people will have a harder time with this than others and you don't want to make anyone feel badly. I have found a "if you can but no more than $20 dollars" a little kinder than the "between $25 and $40 dollars per family" requested this year.
3) Don't "cover" people who haven't chipped in then grouse about it later. People have things you don't know about going on or are just plain busy and will forget to chip in - just expect that to happen. There is no "magic number" that must be reached at any cost.
4) Don't write down each person's name and the exact amount of their contribution when they hand it to you. It's uncomfortable for everyone.
5) Get out there with a card for everyone to sign early on too. The card has nothing to do with chipping in. Everyone's name needs to be on it and the present to be from everyone regardless of monetary contribution.
6) Yes, you will have to linger by the classroom at drop-off and pick-up plus send around a reminder email before it gets down to the wire.
7) Get another parent to collect with you as a team, and split the work.
8) Remember - teachers work hard and deserve our thanks and acknowledgment, not just at the holidays but all year round.

If anyone has additional tips they are very welcome!