Find a daycare center with a largish parking lot, so people dropping off their kids often park a little ways away from the entrance.
Focus on women who are dropping off their kids. Watch for purses (known in some subcultures as “pocketbooks” or “bags” … it’s like a “manbag” only for girls). Most women carry one. If you see a woman bringing the kid(s) to the daycare without the purse, that means there is a purse in her car. Also, if you’ve watched the daycare for a few days you’ll know the minimum amount of time you’ll have to extract the purse from the car.
There will be certain times of day when lots of people are dropping their kids off, or picking them up. This means that there may be moments when there are several targets — cars left by purseless women — available at once, and it also means that there will be people walking back and forth in the parking lot so you can blend in as you move in for your quarry.
Be patient. Walk through the lot, as though you are going somewhere, in such a way that passes by two or three different potential targets. Check the car door of each target to see if it is unlocked. The car doors will be unlocked far more often than usual. This is especailly true of older cars in certain parts of the country where there are still a lot of manual locks. People who are picking up their kids don’t want to mess with the key and the lock when they return to the car, squirming toddler or sleeping baby in their arms. Even people dropping their kids off will often not lock their car. A daycare center is a place where trust has developed in people’s minds (or they would not be there) and this tends to extend outward beyond the confines of the daycare center itself.
So, as you check each car to see if it is unlocked, most won’t be unlocked but there will be more than you might expect. Don’t worry if you don’t get an unlocked car you first few passes through the lot. If you check cars two or three times every morning and two or three times every afternoon, you’ll probably get in a car a half dozen times in a week. Then, you must take the checkbook and/or wallet out of the purse and leave the rest of the purse in place. This way, your success won’t be reported until later.
At some point, you will notice people in the parking lot looking around suspiciously when they leave their cars, and diligently locking them. This means that the word has gone out that you are in business at that particular location, so move to the next nearest daycare and continue hunting.
Do read the morning local paper (on line is the best way) regularly. At some point there will be an article explaining how this all works, as though the police just discovered this tactic, and the article will inform more people about how to not get their checkbooks stolen. Don’t let any such article deter you, though, people are basically stupid and manage to stay uninformed. The article is just there for your amusement.