Do you mean like coupon codes for online ordering or the kinds of coupons that you obtain online but print out for use in stores?
If it's the former, I don't keep track. I just use sites like Flamingoworld.com or fishingfordeals.com to handle them for me. They're searchable and have the up-to-the-minute codes.
If it's the latter, I try to print as I see them and file with my usual coupons in my little file box. One of my local markets (Krogers) no longer accepts coupons printed at home for reasons of "fraud". I don't see how it's different if my, say, Stonyfield Farms coupon was printed at home versus printed in my local paper but Kroger won't take it - even if it has a UPC that scans correctly. Do figure.