This page assumes you have a copy of Sarah Goslee's Basic Tablet Weaving class handout. That handout was designed for students who could watch Sarah demonstrate in front of them. What this page seeks to do is further explain card weaving as described in the handout when there is no experienced person available to provide a demonstration.
The explanation below relies on terminology found in the handout. I may eventually provide a completely independent page, but, I do not have the time or knowledge to do so presently. Besides, Sarah has done a fine job with her handout already!
Start with 10 cards. They each have four holes in them (they may also have a hole in the very center of each card, just ignore that for now). 10 cards times 4 holes = 40 cords. Cut 40 cords about 2 or 3 feet long (we're going to start you with a very short piece, so you can understand the principles). The easiest way to do this is to set two sturdy items 2 or 3 feet apart and wrap the cord back and forth between each item. For instance, you can put two chairs apart three feet apart and put a load of books on them to weight them down.
Now take your cord and go back and forth around the seatbacks of the chairs twenty times. Snip the cord from the spool. Grasp the wrapped cords, still on the chairs, tightly in the middle. Hook your foot around a chair leg and drag it closer to the other to let in some slack. Carefully lift off the cords and put each hand inside and stretch them out. Cut through all the cords at each end, giving you 40 cords roughly the same length.
Pick up four cords from your pile. Pick up a card from the card pile, decide which is the 'front' and which is the 'back' (doesn't matter, just pick one and stick to it), and insert one cord through each hole in the card, from the front to the back. Grab all four cords in the back of the card and tie and overhand knot. Lay this aside neatly, right side up. Repeat with the other 9 cards and 36 cords.
Now, pick up your 10 cards carefully, and pull all the cords from the front so that the knots are snug up against the back of the cards.
Take a rubber band, and from the back, slip it over your deck of cards so that if you drop them now, you won't be upset at the mess on the floor. As far as the hole in the middle of the cards goes, if you don't want to use a rubber band to hold your cards together, you can run a string through the middle of all the cards and tie it together when you take a break. Take a marker and color a stripe on the top edge of the cards. Using your fingers, comb down the loose cords that are hanging from the fronts of the cards and tie them all together in an overhand knot. Now, slide all the cards forward up against this new overhand knot you just tied. Grab all the little overhand knots from the back and tie them in one big overhand knot (without undoing the little knots). Using a scrap piece of cord, tie this new overhand knot to a closet doorknob, or something that isn't going to move soon.
Take the big overhand knot that is in the front of the cards and another piece of scrap cord, and tie it to you. You can tie it to a belt buckle, a pants belt loop, around your waist, whatever. Lean back a little to put tension on the whole apparatus.
Now, slide your cards about 5 inches away from you, and flip the left edge of the cards toward you, the right edge away, keeping your marker strip on the top (in all likelihood, this probably will happen on its own when you apply tension by leaning back). You now have ten cards threaded with a "Z" twist and are ready to go!
Take off the rubber band and slide the cards back and forth with your hands until you can easily see that two holes (and their cords) are on top, and two are on the bottom. The space between the top and the bottom is the shed. Place a ruler, popsicle stick, whatever, in the shed between you and the cards. Turn the pack of cards, as a unit, away from you once. That means the marker stripe is now facing away from your body. Throw your shuttle through the shed, turn again away, and beat. Keep throwing and beating.
Experiment with four turns away from your body, four turns toward your body. You will be able to clearly see the way the pattern changes.
A page with visual examples of different threading and turning techniques is the Tablet Weaving Information page.