I have made a more intentional effort to stop using plastic bags when I shop. I find this much easier to do when I go grocery shopping versus when I stop for a few items at a smaller store. In making this switch, I've found a few things that I like about reusable bags, and I few things I don't and have taken these things into account when making my own bags. I've found that I like a bag that is big, but can fold down into a small square. It's much simpler to use a reusable tote when I'm at a quick stop if I have one in my purse ... but not convenient at all if that tote takes up my whole purse. I'm also a sucker for something that has a little personality, something that looks better than the average reusable bag, something that I enjoy .... well, toting!
My favorite usable bag is one that I bought from Michaels so, when I made mine, that was the pattern I used. The sides and bottoms are one long strip (7" across & 46' long). The other two main pieces are the front and back (they measure 17" deep & 13" across). In order to connect the sides and back a single folded 1/2" binding is used. I made the handles 20" long & 1" across.