I do keep my all of my coupons in my purse at all times. I've been out and not had them and found the item on sale. :(
I shop online before I go to the store because I can see our store's prices on the website. I pick our meals based on the coupons/sales and write our meals out on my shopping list (which I type out by department). We usually shop around midnight since my husband works until 11 (I work days) so it is quieter then.
When I think of something I don't want to forget, I email myself. That way I have the "note" at home or work and won't forget. If I'm working on a list, I'll have my husband email me anything he thinks of from home.
My house is a wreck and I'm terribly disorganized, but I have the heart of an organized person. :) If it helps, I work full-time, 9-5 M-F, my husband works full-time 3-11 Sun-Thurs. I do not carry a diaper bag anymore, just my purse, so EVERYTHING is in there--my wallet, checkbook, coupons, diapers, wipes, extra baby clothes, spit cloths, toys, work that I'm going to do at home, work ID, snacks for me, snacks for kids, lists (I keep a mini-notebook in there but usually forget to use it), you get the idea. My kids are 4 1/2, 3, and 6 months, so I only manage with our schedules to be organized behind the scenes, somewhat. I have no idea what checklist is, or did you mean making a checklist? Good luck! I'd suggest putting any meal or haircut coupons right in your wallet so you always have them with you, too.