I have a problem with regular notebooks. Unless they are dedicated to a singular purpose, I usually fill them up with information that has no long-term significance. My initial solution was to use disc-bound Circa and Arc notebooks for everyday use but found them to be both bulky and heavy to carry around.
I decided that a better solution would be to create a notebook that would allow me to carry loose papers that could be easily rearranged and discarded when no longer needed. These days, most of my important archival information is in Evernote and I either transfer the information from my written notes manually or take a quick photo of the written page with my tablet or phone and store it electronically in Evernote.
I ordered a nice piece of tooling leather from eBay, cut it down to 8.5" x 11" and dyed it. I added an elastic band to hold everything together. It is similar to a traveler's notebook and very quick and easy to make -- less than an hour from start to finish. I custom cut the blank pages down to 8" x 4.75" so that they fit comfortably.
So far, I am very happy with the result. This notebook allows me to use any kind of paper that I want and to mix and match lined paper, grid paper, and various weights of regular copy paper. I can even include receipts, index cards or any other stray bits of paper that I encounter.