Remember not all old paper is valuable. When eyeing a stack of NGs consider that once past the mid-1940s you're looking at a magazine that had circulation of over 2 million copies a month, so the chance that any of it will be scarce, decreases proportionally.
Taking these and other magazines apart either individually or as bound volumes is not easy. It’s time consuming and it has to be done carefully. I like to work in batches of five or ten at a time.
My tools include drop cloth, pliers, small screw driver with a broad flat thin tip, clear plastic page protectors with 3 holes that open at the top, soft pencil with a soft point, sharp utility knife and steel edge ruler to trim the disbound edge. If small repairs are needed I like Filmoplast, a matte finish almost invisible archival tape. If you’re going to interleave any of the sheets be sure to use an acid free paper, and please: No scotch tape.
Put the drop cloth down because there will be lots of old glue, paper chips and nasty fragments of old staple tips. You do not want to get these into your hands, feet or posterior, your carpet, upholstery, floor or the feet of your pets -- very unpleasant.
Before you start taking the magazines apart, go through each one with your soft pencil and put the date on the first page of every article and on every page of the ads lightly and unobtrusively in pencil.
If you’re dealing with NG or any magazine of that era there’s usually a staple or sewing. With NG the staple closure is underneath the back cover. Remove the back cover, then gently pry up the staple tips using the thin flat edge of your screwdriver and straighten them with pliers so they point straight up or break off. Turn the magazine over, remove the front cover. Then gently start lifting the staple up from the front until enough is up to pull out with the pliers. This is harder than it sounds and it has to be done carefully and slowly. If the staple won’t come out - don’t gouge the paper, grab it with the pliers and rock it back and forth until it breaks. Then gently take the pages off and separate them into piles. Toss the stuff you don't want. Save the other material and put articles into individual sleeves and insert into three ring binders.
Keep your broken parts in a cool, dry place, away from direct sunlight and avoid areas that have big changes in humidity. Check your binders at least once a year for bugs and other critters. After you catalog them stick a copy of the description into the sleeve.