Last coupon I got in email was the $25 shipping. If you got it then you're at least on their mailing list. That is the first tip. Get on their email list. The other is that one of the woodworking magazines sometimes has 10% off coupons attached to the front of the subscribers version (not the newsstand version) of their magazine. Can't remember for sure but I think it is Woodworker's Journal. Haven't seen one of those in a while.
I occasionally get a flyer with sale items but not the 10% off everything really valuable coupons.
$25 shipping can be a big discount on the really heavy items.