Cut Some, Leave Some
I'm sure there are plenty of other inbetween methods, but this is what I have settled on and works well for me.
Before I file my whole Sunday coupon inserts, I cut out these coupons:
* Ones that are very likely to be needed
(I base it on knowledge of usual sales, products I would buy anyway, freebies, very high value coupons, etc.)
* Chilled food that I use like deli meat, yogurt, cheese, etc.
(They are often marked down for quick sale and I want my coupons with me.)
(Sales vary so much that you never know exactly what's included and they're often found on clearance.)
I cut these and file them in an envelope that I always carry with me.
I like this method because I have the best of the best with me, yet my other coupons are available when I see a great sale that comes up. I can cut those before I shop and I'm set. I do miss out on some clearance or other deals I discover when I'm at the store, but I figure it's a small price to pay for all the time I save cutting, filing, and getting rid of coupons I don't end up using.