Can Fan/filter question?

After talking to a guy at my local store and reading a bit I am confused about the air flow for a can fan.

I have a can filter, can fan and 1000w light. The ducting goes to the attic. Do I want the fan pulling air from the can filter and through the light or pushing air through the light?

ii have mine setup so that it is pulling the air thru the filter.. i have the filter first, ducting, then the fan on the top end pulling it all.. i think you can set it up anyway that you want to really... this is just the way the guy had his in the store, and what works best for my area....

It's more efficient to pull air rather than push it.