I was thinking today as to some of the things that have helped me become savvy in terms of price comparing while making sure that I go home with only the items that I actually need or planned to buy. A big reason is the public transit tickets here and how you have an hour and a half to travel with it. These tickets ranged from about $2 to $4 depending on what zone you were travelling in. Basically, to me it felt really wasteful if I had to pay say another $4 just because I was shopping too slow and so I always wanted to use the same ticket travelling both ways.
As a result, the only real way to be sure is that I had to do my research ahead of time while make a list of exactly what I was going there for. When you think about it, if you were were driving like the car and parking at the mall there is usually no urgency or incentive for you to get out there quick as most of them offer free parking. For the most part, that habit of researching ahead of time has stuck with me since then.
I guess essentially the key is to make sure you have something that is giving you a genuine incentive to leave within a certain amount of time when it comes to shopping to encourage a more productive and savvy shopping experience where you will actually plan ahead.