Plan your project. Decide on the colors, pattern, length and width of the finished piece. Select your yarn, keeping in mind that fabric woven on a tape loom is usually warp-faced rather than weft-faced, so the vertical warp yarn will dominate. Experiment on paper until you are happy with your design. A good set of colored pencils comes in handy during this part of the process.
Measure and cut the warp yarn. To determine the appropriate length, add 3 feet to the length of the project. The added length is necessary to account for "take-up" during weaving, plus tying-off and finishing. Cut enough warp strands to cover the desired width of the piece. Every yarn has a specific "wpi," or "warps per inch." This figure lets you know how many warp threads you will need per inch of fabric.
Warp your tape loom by tying each piece of warp yarn onto the spool. Bring each warp thread through a slot or hole in the heddle. Then pull the warp yarn tightly enough to hold it taut, yet not tightly enough to cause breakage, and wind the yarn onto the spool. Keep the threads from becoming tangled by using a comb. Tie the bundle of warp threads into an overhand or weaver's knot when approximately 24 inches of yarn remains unwound.
Fill your shuttle with weft yarn by winding the weft yarn onto the shuttle, leaving a small amount of yarn unwound. Estimate how much yarn to leave hanging by visually adding the width of your piece, plus a bit extra for maneuverability.
Grasp the knot at the end of the warp yarn and pull tightly enough to create a firm, even tension. Make a "shed" through which to pass the spool of weft yarn by lifting the heddle, leaving a bit of yarn hanging outside the shed. Weave the next row by moving the heddle down, which creates another shed through which to pass the spool, this time in the opposite direction. Continue to weave, alternately moving the heddle up or down, passing the spool through in one direction and then the other. Keep the fabric smooth by packing the rows together with the shuttle -- or a kitchen fork or comb -- as you weave.
Remove the finished fabric from the loom. Then, knot the dangling warp threads together to form a fringe and keep the piece from unraveling. Depending on the nature of your project, add a belt buckle, or finishing touches such as beads or found objects.