Try the website for the outlet mall you are going to go to. They often have coupons available if you sign up for their email list or even on the site. I've also heard of them have coupons available in the outlet mall office too.
Ikea doesn't really have coupons. They do have their Ikea family club where you get special pricing on merchandise (basically the same thing as a grocery club card).
Go to each store's website and subscribe for their emails. I get Gap Factory store coupons via email all the time. This past weekend was awesome because the store was 50% off plus I had a coupon for extra 15% on top of that. I have found the emails directly from the stores to be the best coupon source.